Sage Journals: Discover world-class research

Abstract

Cardiovascular disease is the leading cause of morbidity and mortality for both men and women in the USA. However, there are differences between the sexes in age-dependent onset, severity, symptoms and outcomes. Basic research into the causes of sex-dependent differences in cardiovascular disease is ongoing and includes investigation into genetic variation in expression and distribution of receptors for the sex steroids; specificity of natural and synthetic ligands that activate the sex steroid receptors; and intracellular mechanisms that are activated by the receptors in all components of the vessel wall and blood elements, which integrate to regulate vascular tone, vascular repair and remodeling in health and disease. In this era of personalized medicine, basic research into mechanisms of sex differences in vascular function will result in improved prevention, detection and treatment of cardiovascular disease in both men and women.

Keywords

cardiovascular disease endothelial cells estrogen genetic polymorphisms Kronos Early Estrogen Prevention study testosterone Women's Health Initiative

There is good news: according to the latest statistics from the American Heart Association (AHA), the mortality from cardiovascular disease in the USA has declined by 29.2% between 1996 and 2006 [1]. However, the bad news is that the death rate from cardiovascular disease for women continues to exceed that of men [1]. What are the reasons for this difference? Does it reflect differences in knowledge and attention to symptoms, access to care, or quality of care delivered to women [1 –4]? What are the defining biological factors contributing to sex differences in risk, presentation, and progression of cardiovascular disease? Studies in humans and animals identify important differences in the function of the vascular endothelium and smooth muscle between males and females, including differences in the production of endothelium-derived vasoactive/proliferative factors, responsiveness of the vascular smooth muscle to these endothelium-derived factors, sympathetic adrenergic neurotransmission and activation and adherence of blood elements to the vascular wall [5 –19]. Dysregulation of these processes contributes to the development of hypertension, ischemia and atherosclerosis leading to myocardial infarction and stroke. Owing to the fact that the incidence of cardiovascular disease occurs in men at earlier ages than in women, and because the incidence of cardio vascular disease increases in women after menopause and is reduced in postmenopausal women who are using hormone therapy to relieve symptoms of menopause, it was hypothesized that the sex steroid estrogen was protective against progression of cardiovascular disease [20 –24]. This article will expand upon this hypothesis by examining the interactions between genetic and hormonal factors contributing to sex differences in vascular function, discuss ongoing research into the effects of hormonal treatment and cardiovascular disease in menopausal women and identify the challenges remaining for cardiovascular research in order to reduce sex disparities in the prevention, diagnosis and treatment of cardiovascular disease.

Genetics of sex differences

What are often defined or categorized as sex differences in vascular functions result from interactions of hormonal milieu with gene expression on the sex chromosomes and autosomes. Therefore, it is important to determine whether a particular characteristic can be attributed to the compliment of sex chromosomes alone or the actions of gonadal steroids (hormonal status) at the time of testing, or hormonal effects on sexual differentiation during development or environmental influences that might impact sexual differentiation and hormonal status [25]. While new animal models are being utilized to investigate these determinants [26], these have not gained widespread usage, nor were they available at the time many studies examining sex differences in vascular function were performed. However, even today, basic science and preclinical studies to investigate causation and examine treatments for cardiovascular disease are not being designed with consideration to the sex, age and hormonal status of the experimental animals. Furthermore, experiments using cells in vitro to assess intracellular signaling pathways often do not identify the sex of the cells; thus, it is not possible to determine which, if any, particular pathways demonstrate differences based on the sex or hormonal status of the cells or donors [27 –30].

Sex versus gender

The Institute of Medicine report ‘Exploring the Biological Contributions to Human Health: Does Sex Matter?’ differentiates the term gender from sex by the socio/psychological factors that influence how an individual perceives him or herself within the context of society [31]. Male and female sex, then, is defined genetically by the sex chromosomes (XX or XY) and the development of functional reproductive organs. This distinction is important because every cell has a sex that is defined by the pair of sex chromosomes it contains.

Cardiovascular risk & Y chromosome

Perhaps the most well-studied gene on the Y chromosome associated with cardiovascular risk is the Sry gene, which initiates development of the testes but is also associated with etiology and severity of hypertension in males [26,32]. The Sry gene modulates tyrosine hydroxylase, which is the enzyme required for the conversion of tyrosine to dihydroxyphenylalanine. This is a major pathway in the synthesis of norepinephrine, the primary neurotransmitter of the sympathetic nervous system (Figure 1) [32]. Thus, it might be predicted that sympathetic activation in males would differ from that of females, which is indeed the case. Hypertension develops sooner in males than in females and may be characterized by greater increases in diastolic pressure [18,32 –36].

Figure 1.

Integrated actions of sex steroids on the control of vascular function.

Cardiovascular risk & the X chromosome

Any genetic polymorphisms of genes expressed on the somatic region of X chromosome will be expressed in males but will show mosaic expression in females owing to heterogeneous inactivation of one X chromosome [37]. This mosaic expression will include those genes implicated in the development of cardiovascular disease such as those encoding small integrin binding N-linked glycoproteins necessary for cell attachment, binding of growth factors and mineralization of extracellular matrix. These processes are involved in development of myo/intimal hyperplasia and calcification of the vascular wall [25,38,39]. However, experiments designed to investigate these and intracellular signaling pathways implicated in the development of vascular disease processes often utilize human umbilical vein endothelial cells, human cells purchased from commercial suppliers, or cells from transgenic animals without regard for the sex or origin of the tissue. Therefore, sex differences in phenotypes associated with activation and expression of these molecular phenotypes have not been evaluated systematically.

Hormonal status affects vascular function in part through binding of the sex steroids to specific receptors, which themselves activate or repress transcriptional activity in target cells including the endothelium and vascular smooth muscle. The gene for the androgen receptor is located on the X chromosome. The CAG repeat polymorphism on exon-1 of the gene encodes the transcriptional regulatory domain of the androgen receptor. The length of this domain is inversely correlated with transcriptional activity of the receptor. In adolescent and adult males, shorter repeat segments (associated with greater androgen receptor activity) are associated with lower levels of high-density lipoprotein (HDL), increased intra-abdominal fat, lower estrogen levels, reduced endothelium-dependent vasodilatation, elevated blood pressure and high sympathetic vasomotor tone [40 –45]. Although there are inconsistent reports regarding the relationship of these repeat segments with the frequency of coronary artery disease and the incidence of myocardial infarction [40,41], these phenotypes fall within the list of canonical risk factors for cardiovascular disease.

Positive associations related to CAG repeat frequency and free testosterone levels have been identified in women with polycystic ovarian syndrome and in some but not all ethnic groups [46 –48]. Women with polycystic ovarian syndrome are at increased risk for cardiovascular disease related to dyslipidemia, glucose intolerance and metabolic syndrome, which is similar to the phenotypic characteristics of men with short CAG repeats [49,50]. Analysis of the CAG repeated regions were not associated with changes in either HDL, blood pressure or sympathetic activation in young, healthy women, which may reflect dilution of repeat effects due to X inactivation as results are expressed using the mean of the two alleles of the polymorphism in the analysis, as it is not possible to determine which allele might be expressed in a particular tissue [45].

Cardiovascular risk & the autosomes

It is now clear that sexually dimorphic expression of genes extends to those located on autosomes; for example in mice, there is sexually dimorphic expression of genes in the liver and adipose tissue affecting steroid and fatty acid metabolism, lipid metabolism and immune responses (Table 1) [51]. Since these tissues impact key risk factors in development of the atherosclerosis, such as hyperlipidemia, inflammation and insulin resistance, similar sexually dimorphic gene expression in humans would explain, in part, the sexual disparity in the development and progression of atherosclerosis. Analysis of 60,000 genotypes in white Americans provides evidence that genetic polymorphisms in individuals with hypertension segregate according to sex, such that in women, polymorphisms in β₁- and α₂-adrenergic receptors were associated with hypertension; while haplotypes for β₂-adrenergic receptors and angiotensinogen were associated with hypertension in males (Figure 1) [52]. These differences would most likely affect responses to hypertensive therapies. Indeed, women have more tachycardia to β-blockers than men [53]. In the future, cost-effective mechanisms to assess such differences might be used to better direct therapy.

Table 1.

Functional categories of genes showing sexually dimorphic expression in liver and adipose tissue of male and female mice.

Fold change in expression	Liver	Adipose
>1.2	Protease inhibitorSteroid hydroxylaseDefense responseImmune responseFatty acid metabolismCarboxylic acid metabolism	Calcium/metal ion bindingIon cation transporterOxidoreductase activityCell motility/adhesionImmune response
>2	Electron transport	Morphogenesis
>3	Monoxygenase activityOxidoreductase activityLipid metabolismSteroid biosynthesisinhibitor activitySerine-type endopeptidaseSteroid metabolism	OrganogenesisMuscle contractionMuscle developmentOxidoreductase activityLipid metabolismC21 steroid hormone iosynthesisC21 steroid hormone metabolismAndrogen and estrogen metabolism Hormone biosynthesis/metabolism

Gene categories in common between tissues are in bold.

Data taken from [51].

While not all genes may show sexual dimorphic expression affecting cellular processes, there is insufficient information to determine whether or not there is sexual dimorphic expression with aging and changes in hormonal status. Therefore, it is important that scientists who utilize in vitro cell systems and experimental animals to simulate disease processes be cognizant of sex and hormonal status as potential variables when designing their experiments and interpretation in order to translate results to humans [29,54]. Furthermore, in clinical trials, representation of women needs to approach the representation of women with a particular condition to ensure sex-specific and evidence-based prevention and treatment recommendations (Table 2) [55].

Table 2.

Relative representation of women in affected patient populations and inclusion in randomized clinical trials of cardiovascular disease prevention.

Condition	Patient population (%)	Inclusion in randomized clinical trials (%)
Hypertension	53	44
Diabetes	50	40
Heart failure	51	29
Hyperlipidemia	46	25
Coronary artery disease	49	28

Data taken from [55].

The sex steroids modulate gene expression on the sex chromosomes and autosomes through specific receptors that bind to nuclear binding domains and modulate gene expression in distinct sequences of cascades, which help to regulate vascular function including lipid metabolism, cell proliferation and growth [56].

Genetics of estrogen receptors

Most effects of the female sex steroids (e.g., 17β-estradiol, estrone and estriol) are mediated through the activation of one of two identified estrogen receptors. Genes for these receptors, α and β, are located on autosomes 6q25.1 and 14q22-q24, respectively [57]. Therefore, polymorphisms in these genes, which dictate receptor integrity, have the potential to impact development of a variety of cellular functions implicated in cardiovascular diseases. The first piece of evidence to link estrogen receptors to cardiovascular disease in humans came from a man with a premature stop codon in estrogen receptor-α. Flow-mediated reactive hyperemia of the brachial artery, indicative of endothelial function, was absent in this man; atherosclerosis was accelerated [58,59]. These observations indicated that estrogen receptor-α contributes to maintaining endothelial function associated with flow-mediated dilatation through the release of endothelium-derived relaxing factor nitric oxide, in males. Subsequent studies support expression of estrogen receptor-α and its modulation by estrogen status in women [19,60].

Estrogen receptor-β shares approximately 97% homology with estrogen receptor-α in their DNA binding domains. Both receptors are expressed in the endothelium and vascular smooth muscle. However, the relative distribution of estrogen receptor-β may be correlated with arterial calcification, hypertension and ventricular hypertrophy [61 –64].

Genetic polymorphisms in estrogen receptors are associated with various risk factors and the risk of cardiovascular disease. Polymorphisms in estrogen receptor-β are associated with estrogen levels in women [65]. Other associations between single nucleotide polymorphisms (SNPs) in either estrogen receptor-α or- β and cardiovascular risk factors in men and women include insulin resistance, diabetes, BMI, hypertension, plasma lipids and endothelial function [66,67]. Although some SNPs associated with estrogen receptor-α were predictive of adverse events in both men and women, adverse events associated with estrogen receptor-β, so far, have been identified only in women (Table 3) [68 –71]. Some polymorphisms of both estrogen receptors that were associated with lipid metabolism were not consistently observed across various racial/ethnic groups in women [72,73]. Therefore, utility of using genotyping of estrogen receptors to assist with clinical diagnosis remains to be realized. Furthermore, the estrogen receptors modulate distinct cellular pathways, some of which regulate cellular metabolism in the mitochondria, and there are insufficient data to extrapolate polymorphisms in each receptor to subtype to these distinct pathways of function [74].

Table 3.

Cardiovascular consequences associated with single nucleotides polymorphisms in estrogen receptors in men and women.

Gene	SNP	Consequence	Ref.
ESRI	rs2234693	Nonfatal MI (m)	[68,199,200]
		Stroke (m)
	rs9340799	Increased risk MI (f)	[71]
	rs2234693	Increased risk fatal IHD (f)
	rs2077647	Augmented arterial tonometry (f)	[77]
	rs2234693
	rs9340799
	rs2234693	Lipid metabolism (f)	[70,73]
	rs9340799
	rs728524
	rs3798577
ERS2	rs1256031	Estradiol levels (f)	[65,66]
	rs1271572	Increased risk MI (f)
	rs1256049	Decreased risk MI (f)
	rs944460	Augmented arterial tonometry (f)	[77]
	rs1256034
	rs1250631	Hypertension/left ventricular mass (f)	[63]
	rs1256059
	rs1255998	Lipid metabolism (f)	[73]
	rs1256065
	rs1256050

f: Female; IHD: Ischemic heart disease; m: Male; MI: Myocardial infarction; SNP: Single nucleotide polymorphism.

Genetics of steroid metabolism

Androstenedione is converted to testosterone by 17β-hydroxysteroid dehydrogenase or to 17β-estradiol (estrogen) by aromatase (CYP19A1) in both men and women. Of the two enzymes, most evaluations of genetic polymorphisms related to cardiovascular risk have focused on aromatase. Two SNPs (rs700518 and rs726547) are associated with the relative ratio of testosterone to estrogen in men [65]. In the Study of Women's Health Across the Nation (SWAN), five different SNPs in the aromatase gene were evaluated relative to serum testosterone:estrogen concentrations. Of these, CYP19 rs936306 showed largest allele frequency in African – American women and was associated with a low testosterone to estradiol ratio [75]. Other polymorphisms of CYP19 are associated with insulin insensitivity and diabetes mellitus in women; both conditions are risk factors for cardiovascular disease [76]. How any of these various SNPs directly affects specific function of the vasculature remains to be determined. In addition, whether changes in the relative concentrations of testosterone to estrogen can be defined as either deleterious or protective to the vasculature will depend, in part, upon the integrity of their respective receptors [77].

Testosterone is also metabolized by 5α-reductase to 5α-dihydrotestosterone, which has a higher affinity than testosterone for the androgen receptor. However, no information is available regarding genetic variation in this enzyme and cardiovascular risk in men or women.

Estrogen (17β-estradiol) is metabolized to catechol estrogens. One such compound, 2-hyrdoxyestradiol, binds DNA-promoting development of tumors [78]. Conversion to 2-methyoxyestradiol by O-methylation catalyzed by catechol-O-methyltransferase (COMT) is considered to be a detoxifying step. COMT is a ubiquitous enzyme and genetic variation in this enzyme affects serum concentrations of 17β-estradiol [79]. In addition, 2-methyoxyestradiol has biological activity (see section ‘Ligand and receptor activating’ below) so that changes in the relative concentrations of the various estrogenic metabolites may affect vascular function in different ways. COMT also degrades catecholamines and thus affects the duration of adrenergic neuronal signaling. Effects of polymorphisms with relationship to cardiovascular disease are unclear at this time, which may reflect the interactions on steroid metabolism and adrenergic signaling, which have not been assessed separately in men and women [80,81].

In addition to specific polymorphisms in enzymes metabolizing sex steroids, copy numbers of these genes may also affect phenotypic responses to the hormones, for example, the activity of hydroxysteroid sulfotransferase (SULT1A1), which is responsible for the conversion of 17β-estradiol to estradiol sulfate and estrone to estrone sulfate, was best related to gene copy number [82]. Whether differences in activity of this enzyme affect hormonally driven cardiovascular phenotypes remains to be determined. However, the possibility that genetic polymorphisms and gene copy number affect responses to drugs (or hormones) suggests that a polygenomic approach may be needed to better understand sex differences in vascular responses [81,83].

Distribution of sex steroid receptors

In addition to genetic differences in structure of the sex steroid receptors, their tissue-specific distribution will also influence sex differences in cardiovascular function. However, few studies have examined or compared the distribution of estrogen receptors in vascular tissue between males and females of specified hormonal status. Estrogen receptors are present in all components of the blood vessel wall: endothelium, smooth muscle and adventitia. In arteries and veins collected as surgical waste from patients undergoing vascular repair, mRNA for estrogen receptor-β was greater than mRNA for estrogen receptor-α and averaged approximately 10–20% higher in tissue from females than males [84,85]. These differences in mRNA for the estrogen receptors are consistent with increased expression of estrogen receptor-β in coronary arteries of men and women. Estrogen receptor-β was greatest in the media compared with either the intima or adventia and was also localized in areas of arterial calcification in arteries from males and females [61,86].

The expression of estrogen receptor-α did not correlate with areas of calcified plaque nor was expression altered with hormone treatment of postmenopausal women. However, expression decreased with age only in postmenopausal women using hormonal treatments [61]. The relative expression of either estrogen receptors did not vary with hormonal treatments in postmenopausal women in any layer of the blood vessel wall when examined by immunohistochemistry [61]. This observation differs from changes in the ratio of estrogen receptor-α to -β evaluated by western blot in aortic endothelial cells derived from pigs following ovariectomy or following treatment of ovariectomized animals with either 17β-estradiol, conjugated equine estrogen or raloxifene [87]. Expression of estrogen receptor-α evaluated by quantitative immunofluorescence in endothelial cells of peripheral veins increased with increasing estradiol during the estrus cycle in premenopausal women and decreased in menopause [60]. Regulation of the expression of estrogen receptors by endogenous and synthetic ligands will most likely be influenced by the concentration of ligand, however, systematic studies are needed for comparison of such variation in males [85,88,89].

The expression of androgen receptors was also greater in the media compared with expression in the intima and adventia of coronary arteries of human males. Expression was negatively correlated with plaque area in diseased coronary arteries [86]. As with variation in expression of estrogen receptors by specific ligands, expression of androgen receptors fluctuate in cerebral arteries of rats following manipulation of endogenous testosterone by orchiectomy and testosterone treatment [90]. It is not known how endogenous fluctuations in testosterone affect androgen receptor expression in human vasculature, or how differences in expression may be related to development of cardiovascular disease. Relationships among androgen receptors with estrogen receptors-α, -β or other steroid receptors (i.e., progesterone or corticosteroids – steroid hormones that are not covered in this article) and their competition for cofactors, which might affect receptor binding to nuclear response element requires further investigation [19].

Most studies have evaluated distribution of sex steroid receptors in conduit arteries prone to atherosclerosis. However, no attention has been paid to their distribution and function in the coronary microvasculature. Such analyses might warrant investigation given that coronary microvascular ischemic disease is more prevalent in women than in men [3,4,91].

Ligands & receptor activation

Endogenous ligands for the androgen receptor (testosterone and 5α-dihydrotestosterone, and the estrogen receptors, 17β-estradiol, estrone and estriol) are present in men and women. Testosterone is produced primarily from the testes in males and 17β-estradiol is produced primarily from the ovaries in females. However, in both sexes, the adrenal glands may also be a source of these hormones and testosterone can be aromatized to 17β-estradiol by other nonreproductive tissue such as the vasculature. Therefore, monitoring concentrations of hormones in the blood provides only a partial indication of the potential concentrations at the target tissue.

Dihydrotestosterone has a higher affinity for the androgen receptor than testosterone [44]; when compared to 17β-estradiol, estrone has greater binding affinity for both the estrogen receptors than estriol [92].

Activation of steroid receptors is independent of genetic sex as is evidenced by hormonal treatments with testosterone or estrogenic compounds to individuals undergoing procedures for gender transformation of female-to-male (FM) and male-to-female (MF), respectively. In terms of cardiovascular function, forearm flow-mediated vasodilatation increased following MF but decreased with FM procedures to levels comparable with that observed in females and males, respectively [93,94]. The incidence of venous thrombosis increases in MF persons to a similar degree to what might be expected in women using exogenous hormone treatments [95,96]. Changes in sympathovagal activation and plasma lipids are also reported in transgendered individuals [97,98]. Adverse cardiovascular events such as stroke and myocardial infarction were more frequent in MF than FM individuals [98]. However, it is not possible at this time to determine whether differences in these thrombotic-associated events reflect the type of hormonal product used, since oral estrogenic products are more thrombogenic than transdermal products, or the result of different hormonal modulation of other processes dictated by an XY genotype or epigenic imprinting [99 –101]. In FM individuals, decreases in HDL and increases in systolic blood pressure are consistent with patterns of lower HDL and higher systolic pressure in males compared with females [1,98]. However, the quality of long-term outcome data in transgendered individuals are somewhat negated by imprecision in data reporting and heterogeneous study designs [98].

Several synthetic compounds termed selective estrogen receptor modulators have been developed with the idea to target the tissue-specific beneficial effects of estrogen. Tamoxifen and raloxifene are two such compounds approved in the USA for women as adjuvant treatment of breast cancer and osteoporosis, respectively. However, both compounds increase the risk of venous thrombosis and neither are as effective as estrogen in relieving symptoms of menopause, nor are they recommended for the prevention of cardiovascular disease [102].

Sex steroids & vascular function

Receptors for sex steroids are distributed at the membrane surface, throughout the cytosol, in the mitochondria and nucleus of cells (Figure 2) [103 –105].

Figure 2.

Genomic and nongenomic mechanisms by which estrogen affects functions of the vascular endothelium and smooth muscle.

There is controversy regarding the exact characterization of estrogen membrane receptors [106 –108]. However, these receptors seem to be present in cells and tissues derived from both males and females [19,94,109,110]. Indeed, acute infusion of estrogen into arteries or when applied to isolated rings of vascular tissue causes dilatation owing to both an increased release of nitric oxide from the endothelium and the inhibition of ion channels in the smooth muscle [64,111 –113 –115].

Whether acute administration of testosterone causes dilatation of the arteries and activates the release of nitric oxide directly through activation of androgen receptors or indirectly through aromatization to estrogen remains controversial [116 –120]. Details regarding specific intracellular signaling pathways leading to steroidal regulation of nitric oxide have been reviewed elsewhere [19]. However, the net effect of testosterone may not enhance nitric oxide production for sustained time periods as does estrogen. Indeed, serum nitric oxide decreases with increasing concentrations of testosterone with puberty in pigs [121] and with hormonal treatment of FM transgendered individuals (see previous section), which, emphasizes the need to distinguish acute nongenomic actions of the sex steroids from genomic actions.

Other endothelium-derived factors affected by sex steroids include angiotensin converting enzyme, endothelin-1, metabolism of arachidonic acid to prostacyclin (predominately in females) or thromboxane (predominately in males) and endothelium-derived hyperpolarizing factor [104,108]. Sex differences in the production of these factors will also have implications for sex differences in response to some therapies used to treat cardiovascular disease, including angiotensin converting enzyme inhibitors, aspirin, endothelin-1 and angiotensin receptor antagonists [53].

In vascular smooth muscle cells, the predominant nongenomic effects of sex steroids include regulation of membrane potential, intracellular calcium concentration and calcium sensitivity of the contractile proteins (Figure 2) [122,123]. These pathways alter vasoconstriction, de-differentiation, proliferation and migration of these cells.

Cytosolic receptors for sex steroids may be involved with post-translational effects, and mitochondrial estrogen receptors have important links to energy production and utilization and production of oxygen-derived free radicals, defining the oxidative stress of cells [90,104,105,124,125].

As discussed in this review, nuclear, genomic effects of the sex steroids are determined by the response elements for receptor binding on specific genes. However, binding of ligand-bound receptors in some cases may require dimerization of estrogen receptors and availability of specific coregulators, which do not show specificity for one steroid receptor compared with another. Therefore, competitive binding for nuclear coregulators will modulate the magnitude of genomic effects in a mixed hormonal environment (e.g., estrogen plus progesterone or testosterone) [19,126 –128].

Protein synthesis modulated by the sex steroids includes production and secretion of matrix proteins including matrix metalloproteinases, matrix Gla, osteopontin and bone scialoprotein [88,129 –133]. These proteins contribute to arterial stiffening and calcification and plaque vulnerability. Vascular repair and angiogenesis are increased by estrogen in part through increases in proliferation of endothelial progenitor cells [134 –139]. In addition, estrogen has anti-inflammatory effects mediated by decreased expression of leukocyte binding sites on the endothelial surface, which limits the attachment and migration of leukocytes during early development of atherosclerotic lesions [140,141].

Metabolic products of 17β-estradiol also have biological activity, which might, in some circumstances act to antagonize the effects of parent compound, for example, the catecholestrogens bind to adrenergic receptors and also compete for COMT that would degrade norepinephrine, thus having the potential to modulate both the magnitude and duration of sympathetic signaling affecting vascular resistance [142,143]. Alternatively, the catecholestrogens are antioxidants, which might potentiate nitric oxide signaling and, along with stimulation of prostacyclin and inhibition of synthesis of endothelin-1 would act to reduce vascular tone. One estrogenic end product of COMT metabolism, 2-methoxyestradiol, inhibits the proliferation of both endothelial and smooth muscle cells. However, it is important to consider that these effects of both the catechol and methoxyestradiols are concentration dependent and affect proliferating cells differently than those that are confluent in an intact vascular wall [144,145].

In order not to oversimplify the actions of the sex steroids, nongenomic and genomic effects of sex steroids are present in all components of the vasculature (e.g., endothelium, smooth muscle, advential fibrobasts and dendritic cells) and blood elements including platelets of males and females.

None of the actions described above occur in isolation and, thus, defining the contribution to testosterone and androgens in the context of vascular reactivity is perhaps more ambiguous than that of estrogen, given the conversion of testosterone to estradiol in males and the differences in reactivity of the androgen receptor based on CAG repeats [43,65,146 –149]. These issues may be important when considering potential cardiovascular side effects of various anti-adrogenic compounds in treating men with prostate cancer [150].

The particular intracellular pathway or mechanism activated or dominated by the sex steroids will be tissue-specific depending, in part, upon the expression of receptors, the concentration of specific ligand and the relative activation of competing agonists acting on converging pathways. Attention to these considerations needs to be incorporated into the design of mechanistic studies, particularly in regard to development of tissue-specific selective (estrogen/steroids) receptor modulators.

While the above discussion focused on components of the vascular wall as targets for the sex steroids, it should be emphasized that steroid receptors and cellular actions of hormones also modulate activity of baro- and chemo-receptors, brain nuclei involved with baroreflex and vasomotor control and production of neurotransmitter at the level of the sympathetic nerve endings (Figure 1). These affects most likely contribute to differences in barosensitivity between males and females and in presentation of vasomotor symptoms in peri- and post-menopausal women [151].

The interaction of platelets with the vascular wall contributes to the development of atherosclerotic lesions [152,153]. Although platelets do not contain a nucleus, genomic activity of the sex steroids are present in platelet precursors, megakaryocytes; thus, the proteomic profile of circulating platelets will vary depending upon the hormonal milieu under which they were produced [154 –156]. Estrogenic treatments reduce platelet aggregation to specific stimuli and their content of platelet-derived growth factor [154,157,158]. Not only are platelets from male animals more sensitive to aggregation than those of females, they also contain more thromboxane, which, if released at a sight of injury, would increase contraction of the vasoconstriction and proliferation of the smooth muscle [159,160]. These observations need to be validated in humans.

Cell membrane-derived microvesicles (microparticles) released from platelets and other cells during activation and apoptosis act as carriers of biological active molecules among cells and are implicated in the development of atherosclerosis and microvascular disease [161 –167]. Although specific studies have not examined differences in production or characteristics of cell-derived microvesicles across the life span in males and females, evidence is beginning to emerge that the number and prothrombic characteristics of microvesicles derived from platelets and endothelial cells change with estrogen status in women [168,169]. Further study is needed to better define how cell-derived microvesicles contribute to sex differences in vascular function.

Sex steroids & prevention of cardiovascular disease

As stated in the initial parts of this review, clinical data provide evidence for earlier development of atherosclerotic disease and hypertension in men compared with women. Owing to the fact that the incidence of both of these conditions increases in women around the time of menopause, it was proposed that female hormones, in particular, estrogen, may be protective against development of atherosclerosis leading to myocardial infarction and stroke. Indeed, results from preclinical, observational and epidemiological studies supported this hypothesis because atherosclerotic-like lesions are decreased in oophorectomized experimental animals treated with estrogen, and adverse cardiovascular events and all causes of mortality are reduced in postmenopausal women who are using menopausal hormonal therapies, women treated with hormones for early ovarian failure and oophorectomized women receiving hormonal treatments [20,170 –173]. However, this hypothesis was not supported by the large randomized clinical trial of hormone treatment for the prevention of cardiovascular disease, the Women's Health Initiative (WHI) [174].

Since women in the WHI averaged 63 years of age, approximately 10 years past the average age of menopause when women initiate hormonal treatments for menopausal symptoms, a new hypothesis called the ‘timing hypothesis’ was proposed. The timing hypothesis states that initiation of hormone treatment early in menopause (or oophorectomy) is required for slowing the progression (preventing development) of cardiovascular disease. This hypothesis is supported by preclinical data in primates and sub-analysis of data from the WHI indicating that treatment initiated within 10 years of menopause (or oophorectomy) provides protection against the development of coronary arterial atheroma, coronary arterial calcification and myocardial infarction [170,175,176,177]. In addition, flow-mediated dilatation declines after 5 years past menopause [178]. An ongoing prospective study testing the timing hypothesis is the Kronos Early Estrogen Prevention Study (KEEPS), in which women are randomized to either placebo, oral conjugated equine estrogen or transdermal 17β-estradiol (with pulsed natural oral progesterone) within the first 3 years of menopause and will continue on treatment for 4 years. Primary outcomes for the study are quantifiable changes in disease progression indicated by changes in carotid intima-medial thickening (by B-mode ultrasound) and coronary calcification (by electron beam computer tomography) [179]. KEEPS will conclude in 2012. This study is important because it is the first randomized trial in which both oral and transdermal treatments can be compared on progression of vascular lesions in two major arteries (carotid and coronary) that are implicated in adverse cardiovascular events (stroke and myocardial infarction, respectively). These comparisons are critical for future prescribing practices since adverse thrombotic events may occur less often with transdermal compared with oral estrogenic products, arteries of differing anatomical origins may differ in susceptibilities for stimuli promoting formation of vascular lesions and effects of hormones on those processes may not be the same [180 –182].

Current prescribing guidelines for hormonal treatments in women do not recommend their use for prevention of cardiovascular disease but for symptoms of menopause at the lowest effective dose for the shortest duration [102,183]. These guidelines may preclude observing any positive effects on the cardiovascular system, since some data suggest that estrogenic protection against cardiovascular disease is evident only when treatment exceeds 5–6 years [184,185]. This may reflect the time course of physiological processes involved with vascular remodeling and soft tissue calcification.

Whether or not exogenous testosterone products promote or protect against the formation of vascular lesions is unclear in part owing to sex-specific effects, dosing regimes and the aromatization of testosterone to estrogen [110,146,147,186 –189]. Furthermore, as mentioned in this review, the integrity of the androgen receptor may determine the overall efficacy of treatment, and perhaps evaluation of this receptor may provide useful information regarding treatment recommendations, for what is now being defined as ‘low T’ in men and the use of testosterone in women at the menopausal transition [190 –192].

Future perspective

In the USA, scientific investigation directed toward understanding the factors contributing to this sex-disparity in cardiovascular disease began in the early 1990s with funding initiatives from the US NIH and political mandates for the inclusion of women in clinical cardiovascular trials [193]. Progress has been slow. Even 10 years following the Institute of Medicine's report ‘Exploring the Biological Contributions to Human Health: Does Sex Matter?’ [31], basic and preclinical research does not consistently consider sex and hormonal status to be important biological variables [29,30,194]. Sex disparities in outcomes, treatment and diagnosis of cardiovascular disease remain as evidenced by the latest statistics from the AHA [1]. Some evidence suggests that the classical risk factors (e.g., age, smoking, systolic blood pressure, diabetes and lipids) may not apply to women as they do in men, particularly in regard to coronary calcification, diastolic heart failure and microvascular disease [195 –197]. New tests are needed to define risk and guide treatment [168,198].

Organizations such as the Organization for the Study of Sex Differences [301] and The International Society of Gender Medicine are establishing the study of sex/gender differences as a scientific discipline by bringing together outstanding basic, translational and clinical scientists who investigate these differences in a systematic way. Efforts such as these will establish sex/gender as scientific variables defining scientific excellence in study designs, research funding priorities, reporting of data and publication. Initiatives such as the Patience Center Outcomes Effectiveness program in the USA and treatment guidelines cannot continue without sound data based on sex as a variable.

Executive summary

Mortality from cardiovascular disease is greater for women than men.

Study of the biological basis of sex differences in factors contributing to development of cardiovascular disease is in its infancy, but sex/gender based medicine is being established as a scientific discipline.

Both the complement of sex chromosomes as well as sex hormones influences expression of autosomal genes affecting function of all elements of the cardiovascular system. Hormonal status interacts with the genetic complement over the life time to modulate development of cardiovascular disease as well as efficacy of treatments and outcomes.

The current treatment guidelines do not recommend the use of menopausal hormones for prevention of cardiovascular disease in women. However, these recommendations for the lowest dose for the shortest period of time may preclude cardiovascular protection, which may not be manifest until after 5 years of use.

Anti-androgenic treatments to men need to be evaluated with consideration of cardiovascular risk.

Sex and hormonal status are important biological variables that will be used to define scientific excellence in design of basic science and clinical trials, in the reporting of results and in the development of treatment guidelines for cardiovascular disease.

Footnotes

VM Miller is supported by grants from the Kronos Longevity Research Institute, the National Institutes of Health and Mayo Clinic. VM Miller is also President of the Organization for the Study of Sex Differences, serves on the board for the Society of Women's Health Research and is a member of the Society of Women's Health Research Isis Cardiovascular Research Network. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

References

Papers of special note have been highlighted as:.

of interest

of considerable interest.

Lloyd-Jones

Adams

Brown

: Heart disease and stroke statistics-2010 update: a report from the American Heart Association. Circulation 121(7), 46–215 (2010).

Latest statistics from the American Heart Association.

Gochfeld

: Sex-gender research sensitivity and healthcare disparities. J. Womens Health 19, 189–194 (2010).

Excellent perspective on the need for attention to sex as a scientific variable in clinical trials.

Shaw

Merz

Bairey CN

Pepine

: Insights from the NHLBI-sponsored women's ischemia syndrome evaluation (WISE) study: part i: gender differences in traditional and novel risk factors, symptom evaluation, and gender-optimized diagnostic strategies. J. Am. Coll. Cardiol. 47, 4–20 (2006).

Merz

Bairey CN

Shaw

Reis

: Insights from the NHLBI-sponsored women's ischemia syndrome evaluation (WISE) study: part ii: gender differences in presentation, diagnosis, and outcome with regard to gender-based pathophysiology of atherosclerosis and macrovascular and microvascular coronary disease. J. Am. Coll. Cardiol. 47, 21–29 (2006).

10.

Barber

Burnett

Jr Miller

: Gender differences in relaxations evoked by C-type natriuretic peptide in porcine coronary arteries. Endothelium 2, 2 (1995).

11.

Barber

Miller

: Gender differences in endothelium-dependent relaxations do not involve NO in porcine coronary arteries. Am. J. Physiol. 273, 2325–2332 (1997).

12.

Brandes

Mugge

: Gender differences in the generation of superoxide anions in the rat aorta. Life Sci. 60, 391–396 (1997).

13.

Lawrence

Leifer

Moura

: Sex differences in platelet adherence to subendothelium: relationship to platelet function tests and hematologic variables. Am. J. Med. Sci. 309, 201–207 (1995).

14.

Maddox

Falcon

Ridinger

Cunard

Ramwell

: Endothelium-dependent gender differences in the response of the rat aorta. J. Pharmacol. Exper. Ther. 240, 392–395 (1987).

15.

Nathan

Pervin

Singh

Rosenfeld

Chaudhuri

: Estradiol inhibits leukocyte adhesion and transendothelial migration in rabbits in vivo. Possible mechanisms for gender differences in atherosclerosis. Circ. Res. 85, 377–385 (1999).

16.

Lamping

Faraci

: Role of sex differences and effects of endothelial NO synthase deficiency in responses of carotid arteries to serotonin. Arterioscler. Thromb. Vasc. Biol. 21, 523–528 (2001).

17.

Knot

Lounsbury

Brayden

Nelson

: Gender differences in coronary artery diameter reflect changes in both endothelial Ca2+ and ecNOS activity. Am. J. Physiol. Heart Circ. Physiol. 276, 961–969 (1999).

18.

Regitz-Zagrosek

Lehmkuhl

Hetzer

: Gender aspects in heart failure. Pathophysiology and medical therapy. Arch. Mal. Coeur Vaiss. 97, 899–908 (2004).

19.

Leung

Jayachandran

Kendall-Thomas

: Pilot study of sex differences in chemokine/cytokine markers of atherosclerosis in humans. Gend. Med. 5 44–52 (2008).

20.

Fortes

Nigro

Scivoletto

Carvalho

MHC

: Influence of sex on the reactivity to endothelin-1 and noradrenaline in spontaneously hypertensive rats. Clin. Exp.Hypertens. A 13(5), 807–816 (1991).

21.

Vincent

Kaiser

Orea

Lodwick

Samani

: Hypertension in the spontaneously hypertensive rat and the sex chromosomes. Hypertension 23, 161–166 (1994).

22.

Muller

van den Beld

Bots

: Endogenous sex hormones and progression of carotid atherosclerosis in elderly men. Circulation 109, 2074–2079 (2004).

23.

Narkiewicz

Phillips

Kato

: Gender-selective interaction between aging, blood pressure, and sympathetic nerve activity. Hypertension 45, 522–525 (2005).

24.

Duckles

Miller

: Hormonal modulation of endothelial no production. Pflugers Arch. Eur. J. Physiol. 459, 841–851 (2010).

25.

Part of a volume dedicated to Robert Furchgott, including a review of both steroidal and protein hormonal regulation of nitric oxide.

26.

Bush

Barrett-Connor

: Noncontraceptive estrogen use and cardiovascular disease. Epidemiol. Rev. 7, 89–104 (1985).

27.

Bush

Cowan

Barrett-Connor

: Estrogen use and all-cause mortality. preliminary results from the lipid research clinics program follow-up study. JAMA 249, 903–906 (1983).

28.

Bush

Barrett-Connor

Cowan

: Cardiovascular mortality and noncontraceptive use of estrogen in women: results from the lipid research clinics program follow-up study. Circulation 75, 1102–1109 (1987).

29.

Adams

Clarkson

Kaplan

Koritnik

: Experimental evidence in monkeys for beneficial effects of estrogen on coronary artery atherosclerosis. Transplant Proc. 21, 3662–3664 (1989).

30.

Clarkson

Prichard

Morgan

Petrick

Klein

: Remodeling of coronary arteries in human and nonhuman primates. J. Am. Med. Assoc. 271, 289–294 (1994).

31.

Arnold

: Sex chromosomes and brain gender. Nat. Rev. Neurosci. 5, 701–708 (2004).

32.

Arnold

Chen

: What does the ‘four core genotypes’ mouse model tell us about sex differences in the brain and other tissues? Front Neuroendocrinol. 30, 1–9 (2009).

33.

Description of animal models to differentiate sex and hormonal effects in experimental animals.

34.

Becker

Arnold

Berkley

: strategies and methods for research on sex differences in brain and behavior. Endocrinology 146, 1650–1673 (2005).

35.

Excellent guide for the design of studies to investigate sex differences, which could be applied to cardiovascular experiments as well.

36.

Liu

Oyarzabal

Yang

Murphy

Hurn

: A novel method for assessing sex-specific and genotype-specific response to injury in astrocyte culture. J. Neurosci. Methods 171, 214–217 (2008).

37.

Wald

: Of mice and women: the bias in animal models. Science 327, 1571–1572 (2010).

38.

Zucker

Beery

: Males still dominate animal studies. Nature 465(7299), 690 (2010).

39.

Wizemann

Pardue

: Exploring the Biological Contributions to Human Health: Does Sex Matter? Board on Health Sciences policy. Institute of Medicine, Washington, DC, USA (2001).

40.

Turner

Farkas

Dunmire

Ely

Milsted

: Which sry locus is the hypertensive Y chromosome locus? Hypertension 53, 430–435 (2009).

41.

Laurent

Albaladejo

Blacher

: Heart rate and pulse pressure amplification in hypertensive subjects. Am. J. Hypertens. 16, 363–370 (2003).

42.

Reyes

Lew

Kimmel

: Gender differences in hypertension and kidney disease. Med. Clin. North Am. 89, 613–630 (2005).

43.

Caplea

Seachrist

Daneshvar

Dunphy

Ely

: Noradrenergic content and turnover rate in kidney and heart shows gender and strain differences. J. Appl. Physiol. 92, 567–571 (2002).

44.

Reckelhoff

: Gender differences in the regulation of blood pressure. Hypertension 37, 1199–1208 (2001).

45.

Avner

Heard

: X-chromosome inactivation: counting, choice and initiation. Nat. Rev. Genet. 2, 59–67 (2001).

46.

Van

Bakalov

Zinn

Bondy

: Maternal X chromosome, visceral adiposity, and lipid profile. JAMA 295, 1373–1374 (2006).

47.

Singh

Petrov

: Evolution of gene function on the X chromosome versus the autosomes. Genome Dyn. 3, 101–118 (2007).

48.

Hersberger

M MJ

Funke

Marti-Jaun

: The CAG repeat polymorhism in the androgen receptor gene is associated with HDL-cholesterol but not with coronary atherosclerosis or myocardial infarction. Clin. Chem. 51, 1110–1115 (2005).

49.

Alevizaki

M CA

Garofallaki

Sarika

: The androgen receptor gen CAG polymorhphism is associated with the severity of coronary artery disease in men. Clin. Endocrinol. (Oxf.) 59, 749–755 (2003).

50.

Zitzmann

Brune

Kornmann

: The CAG repeart polymorphism in the AR gene affects high density lipoprotein cholesterol and arterial vasoreactivity. J. Clin. Endocrinol. Metab. 86, 4867–4873 (2001).

51.

Zitzmann

Nieschlag

: The CAG repeat polymorphism within the androgen receptor gene and maleness. Int. J. Androl. 26, 76–83 (2003).

52.

Jiang

Min IH

: Polymorphisms in androgen and estrogen receptor genes: effects on male aging. Exp. Gerontol. 39, 1603–1611 (2004).

53.

Pausova

Abrahamowicz

Mahboubi

: Functional variation in the androgen-receptor gene is associated with visceral adiposity and blood pressure in male adolescents. Hypertension 55, 706–714 (2010).

54.

Van Nieuwerburgh

Stoop

Cabri

: Shorter CAG repeats in the androgen receptor gene may enhance hyperandrogenicity in polycystic ovary syndrome. Gynecol. Endocrinol. 24, 669–673 (2008).

55.

Ferk

Perme

Teran

Gersak

: Androgen receptor gene (CAG)n polymorphism in patients with polycystic ovary syndrome. Fertil. Steril. 90, 860–863 (2008).

56.

Liu

Hong

Cui

: Androgen receptor gene CAG(n) trinucleotide repeats polymorphism in Chinese women with polycystic ovary syndrome. Endocrine 33, 165–170 (2008).

57.

Wild

Carmina

Diamanti-Kandarakis

: Assessment of cardiovascular risk and prevention of cardiovascular disease in women with the polycystic ovary syndrome: a consensus statement by the Androgen Excess and Polycystic Ovary Syndrome (AE-POS) Society. J. Clin. Endocrinol. Metab. 95, 2038–2049 (2010).

58.

Shah

Antoine

Pall

: Association of androgen receptor CAG repeat polymorphism and polycystic ovary syndrome. J. Clin. Endocrinol. Metab. 93, 1939–1945 (2008).

59.

Yang

Schadt

Wang

: Tissue-specific expression and regulation of sexually dimorphic genes in mice. Genome Res. 16, 995–1004 (2006).

60.

Rana

Insel

Payne

: Population-based sample reveals gene-gender interactions in blood pressure in white americans. Hypertension 49, 96–106 (2007).

61.

Regitz-Zagrosek

: Therapeutic implications of the gender-specific aspects of cardiovascular disease. Nat. Rev. Drug Discov. 5, 425–438 (2006).

62.

Nice review of the differences in therapeutic efficacy of various drugs used to treat cardiovascular diseases in women.

63.

Nieuwenhoven

Klinge

: Scientific excellence in applying sex- and gender-sensitive methods in biomedical and health research. J. Womens Health 19, 313–321 (2010).

64.

Melloni

Berger

Wang

: Representation of women in randomized clinical trials of cardiovascular disease prevention. Circ. Cardiovasc. Qual. Outcomes 3(2), 135–42 (2010).

65.

Schnoes

Jaffe

Iyer

: Rapid recruitment of temporally distinct vascular gene sets by estrogen. Mol. Endocrinol. 22, 2544–2556 (2008).

66.

Enmark

Gustafsson

: Oestrogen receptors-an overview. J. Intern. Med. 246, 133–138 (1999).

67.

Sudhir

Chou

Messina

: Endothelial dysfunction in a man with disruptive mutation in oestrogen-receptor gene. Lancet 349, 1146–1147 (1997).

68.

Sudhir

Chou

Chatterjee

: Premature coronary artery disease associated with a disruptive mutation in the estrogen receptor gene in a man. Circulation 96, 3774–3777 (1997).

69.

Gavin

Seals

Silver

Moreau

: Vascular endothelial estrogen receptor α is modulated by estrogen status and related to endothelial function and endothelial nitric oxide synthase in healthy women. J. Clin. Endocrinol. Metab. 94, 3513–3520 (2009).

70.

Christian

Liu

Harrington

: Intimal estrogen receptor (ER) β, but not ERα expression, is correlated with coronary calcification and atherosclerosis in pre-and postmenopausal women. J. Clin. Endocrinol. Metab. 91, 2713–2720 (2006).

71.

Zhu

Bian

: Abnormal vascular function and hypertension in mice deficient in estrogen receptor β. Science 295, 505–508 (2002).

72.

Peter

I SA

Vasan

Zucker

: Association of estrogen receptor β gene polymorhisms with left ventricular mass and wall thickness in women. Am. J. Hypertens. 18, 1388–1395 (2005).

73.

Traupe

Stettler

: Distinct roles of estrogen receptors α and β mediating acute vasodilation of epicardial coronary arteries. Hypertension 49, 1364–1370 (2007).

74.

Peter

Kelley-Hedgepeth

Fox

: Variation in estrogen-related genes associated with cardiovascular phenotypes and circulating estradiol, testosterone, and dehydroepiandrosterone sulfate levels. J. Clin. Endocrinol. Metab. 93, 2779–2785 (2008).

75.

Rexrode

Ridker

Hegener

: Polymorphisms and haplotypes of the estrogen receptor-β gene (ESR2) and cardiovascular disease in men and women. Clin. Chem. 53, 1749–1756 (2007).

76.

Sowers

Wilson

Kardia

Chu

McConnell

: CYP1A1 and CYP1B1 polymorphisms and their association with estradiol and estrogen metabolites in women who are premenopausal and perimenopausal. Am. J. Med. 119, 44–51 (2006).

77.

Shearman

Cupples

Demissie

: Association between estrogen receptor α gene variation and cardiovascular disease. JAMA 290, 2263–2270 (2003).

78.

Peter

I SA

Zucker

Schmid

: Variation in estrogen-related genes and cross-sectional and longitudinal blood pressure in the Framingham Heart Study. J. Hyperten. 23, 2193–2200 (2005).

79.

Demissie

S CL

Shearman

Gruenthal

: Estrogen receptor-α variants are associated with lipoprotein size distribution and particle levels in women: the Framingham Heart Study. Atherosclerosis 185, 210–218 (2006).

80.

Schuit

Oei

Witteman

: Estrogen receptor α gene polymorphisms and risk of myocardial infarction. JAMA 291, 2969–2977 (2004).

81.

Herrington

Howard

Hawkins

: Estrogen-receptor polymorphisms and effects of estrogen replacement on high-density lipoprotein cholesterol in women with coronary disease. N. Engl. J. Med. 346, 967–974 (2002).

82.

Sowers

Symons

Jannausch

Chu

Kardia

: Sex steroid hormone polymorphisms, high-density lipoprotein cholesterol, and apolipoprotein A-1 from the Study of Women's Health Across the Nation (SWAN). Am. J. Med. 119, S61–S68 (2006).

83.

O'Lone

Knorr

Jaffe

: Estrogen receptors α and β mediate distinct pathways of vascular gene expression, including genes involved in mitochondrial electron transport and generation of reactive oxygen species. Mol. Endocrinol. 21, 1281–1296 (2007).

84.

Excellent study to differentiate distinct actions of the estrogen receptors.

85.

Sowers

Wilson

Kardia

Chu

Ferrell

: Aromatase Gene (CYP 19) polymorphisms and endogenous androgen concentrations in a multiracial/multiethnic, multisite study of women at midlife. Am. J. Med. 119, 523–530 (2006).

86.

Zhao

Scuteri

Brockwell

Sowers

: The association of genetic polymorphisms in sex hormone biosynthesis and action with insulin sensitivity and diabetes mellitus in women at midlife. Am. J. Med. 119, 69–78 (2006).

87.

Peter

Kelley-Hedgepeth

Huggins

: Association between arterial stiffness and variations in oestrogen-related genes. J. Hum. Hypertens. 23, 636–644 (2009).

88.

Cavalieri

Stack

Devanesan

: Molecular origin of cancer: catechol estrogen-3,4-quinones as endogenous tumor initiators. Proc. Natl Acad. Sci. USA 94, 10937–10942 (1997).

89.

Worda

Sator

Schneeberger

: Influence of the catechol-O-methyltransferase (COMT) codon 158 polymorphism on estrogen levels in women. Hum. Reprod. 18, 262–266 (2003).

90.

Hagen

Stovner

Skorpen

Pettersen

Zwart

: The impact of the catechol-O-methyltransferase Val158Met polymorphism on survival in the general population – the HUNT study. BMC Med. Genet. 19(8), 34 (2007).

91.

Tempfer

Riener

Hefer

Huber

Muendlein

: DNA microarray-based analysis of single nucleotide polymorphisms may be useful for assessing the risks and benefits of hormone therapy. Fertil. Steril. 82, 132–137 (2004).

92.

Hebbring

Adjei

Baer

: Human SULT1A1 gene: copy number differences and functional implications. Hum. Mol. Genet. 16, 463–470 (2007).

93.

Zhu

: Catechol-O-methyltransferase (COMT)-mediated methylation metabolism of endogenous bioactive catechols and modulation by endobiotics and xenobiotics: importance in pathophysiology and pathogenesis. Curr. Drug Metab. 3, 321–349 (2002).

94.

Hodges

Tung

Yan

X-D

: Estrogen receptors α and β. Prevalence of estrogen receptor β mRNA in human vascular smooth muscle and transcriptional effects. Circulation 101, 1792–1798 (2000).

95.

Barton

Meyer

Haas

: Hormone replacement therapy and atherosclerosis in postmenopausal women: does aging limit therapeutic benefits? Arterioscler. Thromb. Vasc. Biol. 27, 1669–1672 (2007).

96.

Liu

Christian

Ruan

Miller

Fitzpatrick

: Correlating androgen and estrogen steroid receptor expression with coronary calcification and atherosclerosis in men without known coronary artery disease. J. Clin. Endocrinol. Metab. 90, 1041–1046 (2005).

97.

Okano

Jayachandran

Yoshikawa

Miller

: Differential effects of chronic treatment with estrogen receptor ligands on regulation of nitric oxide synthase in porcine aortic endothelial cells. J. Cardiovasc. Pharmacol. 47, 621–628 (2006).

98.

Rzewuska-Lech

Jayachandran

Fitzpatrick

Miller

: Differential effects of 17β-estradiol and raloxifene on VSMC phenotype and expression of osteoblast-associated proteins. Am. J. Physiol. Endocrinol. Metab. 289, E105–E112 (2005).

99.

Ihionkhan

Chambliss

Gibson

: Estrogen causes dynamic alterations in endothelial estrogen receptor expression. Circ. Res. 91, 814–820 (2002).

100.

Gonzales

Ansar

Duckles

Krause

: Androgenic/estrogenic balance in the male rat cerebral circulation: metabolic enzymes and sex steroid receptors. J. Cereb. Blood Flow Metab. 27, 1841–1852 (2007).

101.

Olson

Kelsey

Matthews

: Symptoms, myocardial ischaemia and quality of life in women: results from the NHLBI-sponsored WISE study. Eur. Heart J. 24, 1506–1514 (2003).

102.

Kuiper

Carlsson

Grandien

: Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors α and β. Endocrinology 138, 863–870 (1997).

103.

McCredie

McCrohon

Turner

: Vascular reactivity is impaired in genetic females taking high-dose androgens. J. Am. Coll. Cardiol. 32, 1331–1335 (1998).

104.

New

Timmins

Duffy

: Long-term estrogen therapy improves vascular function in male to female transsexuals. J. Am. Coll. Cardiol. 29, 1437–1444 (1997).

105.

Toorians

Thomassen

Zweegman

: Venous thrombosis and changes of hemostatic variables during cross-sex hormone treatment in transsexual people. J. Clin. Endocrinol. Metab. 88, 5723–5729 (2003).

106.

Fortin

Klein

Messmore

O'Connell

: Myocardial infarction and severe thromboembolic complications. As seen in an estrogen-dependent transsexual. Arch. Intern. Med. 144, 1082–1083 (1984).

107.

Resmini

Casu

Patrone

: Sympathovagal imbalance in transsexual subjects. J. Endocrinol. Invest. 31, 1014–1019 (2008).

108.

Elamin

Garcia

Murade

Erwin

Montori

: Effect of sex steroid use on cardiovascular risk in transsexual individuals: a systematic review and meta-analyses. Clin. Endocrinol. (Oxf) 72, 1–10 (2010).

109.

Scarabin

Alhenc-Gelas

Plu-Bureau

: Effects of oral and transdermal estrogen/progesterone regimens on blood coagulation and fibrinolysis in postmenopausal women: a randomized controlled trial. Arterioscler. Thromb. Vasc. Biol. 17, 3071–3078 (1997).

110.

JY-P

Chen

M-J

Sheu

WH-H

: Differential effects of oral conjugated equine estrogen and transdermal estrogen on atherosclerotic vascular disease risk markers and endothelial function in healthy postmenopausal women. Human Reprod. 21, 2715–2720 (2006).

111.

Vehkavaara

Silveira

Hakala-Ala-Pietila

: Effects of oral and transdermal estrogen replacement therapy on markers of coagulation, fibrinolysis, inflammation and serum lipids and lipoproteins in postmenopausal women. Thromb. Haemost. 85, 619–625 (2001).

112.

Santen

Allred

Ardoin

: Postmenopausal hormone therapy: an endocrine society scientific statement. J. Clin. Endocrinol. Metab. 95(Suppl. 1), S1–S66 (2010).

113.

Latest practice guidelines on hormone therapy.

114.

Orshal

Khalil

: Gender, sex hormones, and vascular tone. Am. J. Physiol. Regul. Integr. Comp. Physiol. 286, 233–249 (2004).

115.

Miller

Duckles

: Vascular actions of estrogens: functional implications. Pharmacol. Rev. 60, 210–241 (2008).

116.

Comprehensive review of the integrated actions of estrogen.

117.

Duckles

Krause

Stirone

Procaccio

: Estrogen and mitochondria: a new paradigm for vascular protection? Mol. Interv. 6, 26–35 (2006).

118.

Levin

: G Protein-coupled receptor 30: estrogen receptor or collaborator? Endocrinology 150, 1563–1565 (2009).

119.

Excellent review of the controversies related to defining estrogenic membrane receptors.

120.

Moriarty

Kim

Bender

: Minireview: estrogen receptor-mediated rapid signaling. Endocrinology 147, 5557–5563 (2007).

121.

Meyer

Haas

Prossnitz

Barton

: Nongenomic regulation of vascular cell function and growth by estrogen. Mol. Cell Endocrinol. 308, 9–16 (2009).

122.

Sudhir

Komesaroff

: Cardiovascular actions of estrogens in men. J. Clin. Endocrinol. Metab. 84, 3411–3415 (1999).

123.

Bunck

Toorians

Lips

Gooren

: The effects of the aromatase inhibitor anastrozole on bone metabolism and cardiovascular risk indices in ovariectomized, androgen-treated female-to-male transsexuals. Eur. J. Endocrinol. 154, 569–575 (2006).

124.

Williams

Adams

Klopfenstein

: Estrogen modulates responses of atherosclerotic coronary arteries. Circulation 81, 1680–1687 (1990).

125.

Williams

Adams

Herrington

Clarkson

: Short-term administration of estrogen and vascular responses of atherosclerotic coronary arteries. J. Am. Coll. Cardiol. 20, 452–457 (1992).

126.

Williams

Shackelford

Iams

Mustafa

: Endothelium-dependent relaxation in estrogen-treated spontaneously hypertensive rats. Eur. J. Pharmacol. 145, 205–207 (1988).

127.

Prakash

Togaibayeva

Kannan

: Estrogen increases [Ca2+] efflux from female porcine coronary arterial smooth muscle. Am. J. Physiol. (Heart Circ Physiol) 45, H926–H934 (1999).

128.

White

Darkow

Lang

Falvo JL

: Estrogen relaxes coronary arteries by opening BKca channels through a cGMP-dependent mechanism. Circ. Res. 77, 936–942 (1995).

129.

Farhat

Wolfe

Bargas

Foegh

Ramwell

: Effect of testosterone treatment on vasoconstrictor response of left anterior descending coronary artery in male and female pigs. J. Cardiovasc. Pharmacol. 25, 495–500 (1995).

130.

Herman

Robinson

McCredie

: Androgen deprivation is associated with enhanced endothelium-dependent dilatation in adult men. Arterioscler. Thromb. Vasc. Biol. 17, 2004–2009 (1997).

131.

Akishita

Eto

: Androgen receptor-dependent activation of endothelial nitric oxide synthase in vascular endothelial cells: role of phosphatidylinositol 3-kinase/Akt pathway. Endocrinology 151, 1822–1828 (2010).

132.

Webb

McNeill

Hayward

deZeigler

Collins

: Effects of testosterone on coronary vasomotor regulation in men with coronary heart disease. Circulation 100, 1690–1696 (1999).

133.

Yue

Chatterjee

Beale

Poole-Wilson

Collins

: Testosterone relaxes rabbit coronary arteries and aorta. Circulation 91, 1154–1160 (1995).

134.

Chatrath

Ronningen

Severson

: Endothelium-dependent responses in coronary arteries are changed with puberty in male pigs. Am. J. Physiol. Heart Circ. Physiol. 285, 1168–1176 (2003).

135.

Koledova

Khalil

: Sex hormone replacement therapy and modulation of vascular function in cardiovascular disease. Expert Rev. Cardiovasc. Ther. 5, 777–789 (2007).

136.

Yang

Jeon

Baek

: 17β-estradiol attenuates vascular contraction through inhibition of RhoA/Rho kinase pathway. Naunyn Schmiedebergs Arch. Pharmacol. 380, 35–44 (2009).

137.

Jacob

Sebastian

Devassy

: Membrane estrogen receptors: genomic actions and post transcriptional regulation. Mol. Cell Endocrinol. 246, 34–41 (2006).

138.

O'Lone

Knorr

Jaffe

139.

Wierman

: Sex steroid effects at target tissues: mechanism of action. Adv. Physiol. Educ. 31, 26–33 (2007).

140.

Meyer

Haas

Barton

: Gender differences of cardiovascular disease, new persepctives for estrogen signaling. Hypertension 47, 1019–1026 (2006).

141.

Prossnitz

Barton

: Signaling, physiological functions and clinical relevance of the G protein-coupled estrogen receptor GPER. Prostaglandins Other Lipid Mediat. 89, 89–97 (2009).

142.

Great schematics of signaling processes associated with these estrogenic membrane receptors.

143.

Gorodeski

: Estrogen decrease in tight junctional resistance involves matrix-metalloproteinase-7-mediated remodeling of occludin. Endocrinology 148, 218–231 (2007).

144.

Chen

Kelpke

Oparil

Thompson

: Estrogen attenuates integrin-β (3)-dependent adventitial fibroblast migration after inhibition of osteopontin production in vascular smooth muscle cells. Circulation 101, 2949–2955 (2000).

145.

Lewandowski

Komorowski

Mikhalidis

: Effects of hormone replacement therapy type and route of administration on plasma matrix metalloproteinases and their tissue inhibitors in postmenopausal women. J. Clin. Endocrinol. Metab. 91, 3123–3130 (2006).

146.

Greendale

Palla

: The effects of hormone therapy on the markers of inflammation and endothelial function and plasma matrix metalloproteinase-9 level in postmenopausal women: the Postmenopausal Estrogen Progestin Intervention (PEPI) trial. Atherosclerosis 185, 347–352 (2006).

147.

Hwang

Hodis

Hsiai

Asatryan

Sevanian

: Role of annexin II in estrogen-induced macrophage matrix metalloproteinase-9 activity: the modulating effect of statins. Atherosclerosis 189, 76–82 (2006).

148.

Losordo

Isner

: Estrogen and angiogenesis: a review. Arterioscler. Thromb. Vasc. Biol. 21, 6–12 (2001).

149.

Fadini

de Kreutzenberg

Albiero

: Gender differences in endothelial progenitor cells and cardiovascular risk profile: the role of female estrogens. Arterioscler. Thromb. Vasc. Biol. 28, 997–1004 (2008).

150.

Hamada

Kim

Iwakura

: Estrogen receptors α and β mediate contribution of bone marrow-derived endothelial progenitor cells to functional recovery after myocardial infarction. Circulation 114, 2261–2270 (2006).

151.

Bulut

Albrecht

Imohl

: Hormonal status modulates circulating endothelial progenitor cells. Clin. Res. Cardiol. 96, 258–263 (2007).

152.

Imanishi

Hano

Nishio

: Estrogen reduces angiotensin II-induced acceleration of senescence in endothelial progenitor cells. Hypertens. Res. 28, 263–271 (2005).

153.

Imanishi

Hano

Nishio

: Estrogen reduces endothelial progenitor cell senescence through augmentation of telomerase activity. J. Hyperten. 23, 1699–1706 (2005).

154.

Santizo

Pelligrino

: Estrogen reduces leukocyte adhesion in the cerebral circulation of female rats. J. Cereb. Blood Flow Metab. 19, 1061–1065 (1999).

155.

Xing

Nozell

Chen

Hage

Oparil

: Estrogen and mechanisms of vascular protection. Arterioscler. Thromb. Vasc. Biol. 29, 289–295 (2009).

156.

Ball

Knuppen

: Formation, metabolism, and physiologic importance of catecholestrogens. Am. J. Obstet. Gynecol. 163, 2163–2170 (1990).

157.

Paden

McEwen

Fishman

Snyder

DeGroff

: Competition by estrogens for catecholamine receptor binding in vitro. J. Neurochem. 39, 512–520 (1982).

158.

Dubey

Tofovic

Jackson

: Cardiovascular pharmacology of estradiol metabolites. J. Pharmacol. Exp. Ther. 308, 403–409 (2004).

159.

Barchiesi

Jackson

Fingerle

: 2-methoxyestradiol metabolite, inhibits neointima formation and smooth muscle cell growth via double blockade of the cell cycle. Circ. Res. 99, 266–274 (2006).

160.

Liu

Death

Handelsman

: Androgens and cardiovascular disease. Endocr. Rev. 24, 313–340 (2003).

161.

Phillips

: Is atherosclerotic cardiovascular disease an endocrinological disorder? The estrogen-androgen paradox. J. Clin. Endocrinol. Metab. 90, 2708–2711 (2005).

162.

Mukherjee

Dinh

Chaudhuri

Nathan

: Testosterone attenuates expression of vascular cell adhesion molecule-1 by conversion to estradiol by aromatase in endothelial cells: implications in atherosclerosis. Proc. Natl Acad. Sci. USA 99, 4055–4060 (2002).

163.

Zhang

Wang

Jiang

: Effects of testosterone and 17-β-estradiol on TNF-α-induced E-selectin and VCAM-1 expression in endothelial cells. Analysis of the underlying receptor pathways. Life Sci. 71, 15–29 (2002).

164.

Dockery

Bulpitt

Agarwal

Vernon

Rajkumar

: Effect of androgen suppression compared with androgen receptor blockade on arterial stiffness in men with prostate cancer. J. Androl. 30, 410–415 (2009).

165.

Arain

Kuniyoshi

Abdalrhim

Miller

: Sex/gender medicine – the biological basis for personalized care in cardiovascular medicine. Circ. J. 73, 1774–1782 (2009).

166.

Ross

Glomset

: The pathogenesis of atherosclerosis (first of two parts). N. Engl. J. Med. 295, 369–377 (1976).

167.

Ross

Glomset

: The pathogenesis of atherosclerosis (second of two parts). N. Engl. J. Med. 295, 420–425 (1976).

168.

Jayachandran

Mukherjee

Steinkamp

: Differential effects of 17β-estradiol, conjugated equine estrogen and raloxifene on mRNA expression, aggregation and secretion in platelets. Am. J. Physiol. Heart Circ. Physiol. 288, 2355–2362 (2005).

169.

Jayachandran

Karnicki

Miller

: Platelet characteristics change with aging: role of estrogen receptor β. J. Gerontol. Biol. Sci. 60, 815–819 (2005).

170.

Miller

Jayachandran

Owen

: Aging, estrogen, platelets and thrombotic risk. Clin. Exp. Pharmacol. Physiol. 34, 814–821 (2007).

171.

Jayachandran

Owen

Miller

: Effects of ovariectomy on aggregation, secretion, and metalloproteinases in porcine platelets. Am. J. Physiol. Heart Circ. Physiol. 284, 1679–1685 (2003).

172.

Jayachandran

Okano

Chatrath

: Sex-specific changes in platelet aggregation and secretion with sexual maturity in pigs. J. Appl. Physiol. 97, 1445–1452 (2004).

173.

Miller

Lewis

Barber

: Gender differences and endothelium- and platelet-derived factors in the coronary circulation. Clin. Exp. Pharmacol. Physiol. 26, 132–136 (1999).

174.

Lewis

Bracamonte

Rud

Miller

: genome and hormones: gender differences in physiology selected contribution: effects of sex and ovariectomy on responses to platelets in porcine femoral veins. J. Appl. Physiol. 91, 2823–2830 (2001).

175.

Jimenez

Mauro

: Endothelial cells release phenotypically and quantitatively distinct microparticles in activation and apoptosis. Thromb. Res. 109, 175–180 (2003).

176.

Boulanger

Scoazec

Ebrahimian

: Circulating microparticles from patients with myocardial infarction cause endothelial dysfunction. Circulation 104, 2649–2652 (2001).

177.

Tan

Tayebjee

Lim

Lip

: Clinically apparent atherosclerotic disease in diabetes is associated with an increase in platelet microparticle levels. Diabet. Med. 22, 1657–1662 (2005).

178.

Piccin

Murphy

Smith

: Circulating microparticles: pathophysiology and clinical implications. Blood Rev. 21, 157–171 (2007).

179.

Brogan

Shah

Brachet

: Endothelial and platelet microparticles in vasculitis of the young. Arthritis Rheum. 50, 927–936 (2004).

180.

Bernal-Mizrachi

Fierro

: Endothelial microparticles correlate with high-risk angiographic lesions in acute coronary syndromes. Int. J. Cardiol. 97, 439–446 (2004).

181.

Simak

Gelderman

Wright

Baird

: Circulating endothelial microparticles in acute ischemic stroke: a link to severity, lesion volume and outcome. J. Thromb. Haemost. 4, 1296–1302 (2006).

182.

Jayachandran

Litwiller

Owen

: Characterization of blood borne microparticles as markers of premature coronary calcification in recently menopausal women. Am. J. Physiol. Heart Circ Physiol 295, 931–938 (2008).

183.

Jayachandran

Litwiller

Owen

Miller

: circulating microparticles and endogenous estrogen in newly menopausal women. Climacteric 12, 1–8 (2009).

184.

Clarkson

: Estrogen effects on arteries vary with stage of reproductive life and extent of subclinical atherosclerosis progression. Menopause 14, 373–384 (2007).

185.

Kalantaridou

Naka

Bechlioulis

: Premature ovarian failure, endothelial dysfunction and estrogen-progestogen replacement. Trends Endocrinol. Metab. 17, 101–109 (2006).

186.

Rocca

Grossardt

Andrade

Malkasian

Melton

: Survival patterns after oophorectomy in premenopausal women: a population-based cohort study. Lancet Oncol. 7, 821–828 (2006).

187.

Shuster

Gostout

Grossardt

Rocca

: Prophylactic oophorectomy in premenopausal women and long-term health. Menopause Int. 14, 111–116 (2008).

188.

Raises issues related to the practice of prophylactic oophorectomy.

189.

Rossouw

Anderson

Prentice

: Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA 288, 321–333 (2002).

190.

Grodstein

Manson

Stampfer

: Hormone therapy and coronary heart disease: the role of time since menopause and age at hormone initiation. J. Womens Health 15, 35–44 (2006).

191.

Hsia

Langer

Manson

: Conjugated equine estrogens and coronary heart disease. Arch. Intern. Med. 166, 357–365 (2006).

192.

Manson

Allison

Rossouw

: Estrogen therapy and coronary-artery calcification. N. Engl. J. Med. 356, 2591–2602 (2007).

193.

Vitale

Mercuro

Cerquetani

: Time since menopause influences the acute and chronic effect of estrogens on endothelial function. Arterioscler. Thromb. Vasc. Biol. 28, 348–352 (2008).

194.

Harman

Brinton

Cedars

: KEEPS: The Kronos Early Estrogen Prevention Study. Climacteric 8, 3–12 (2005).

195.

Canonico

Oger

Plu-Bureau

: Hormone therapy and venous thromboembolism among postmenopausal women. Circulation 115, 840–845 (2007).

196.

Moreau

Donato

Seals

: Arterial intima-media thickness: site-specific associations with HRT and habitual exercise. Am. J. Physiol. Heart Circ Physiol 283, H1409–1417 (2002).

197.

Hendrix

Wassertheil-Smoller

Johnson

: Effects of conjugated equine estrogen on stroke in the Women's Health Initiative. Circulation 113, 2425–2434 (2006).

198.

Utian

Archer

Bachmann

: Estrogen and progestogen use in postmenopausal women: July 2008 position statement of the North American Menopause Society. Menopause 15, 584–603 (2008).

199.

Toh

Hernandez-Diaz

Logan

Rossouw

Hernan

: Coronary heart disease in postmenopausal recipients of estrogen plus progestin therapy: does the increased risk ever disappear? Ann. Intern. Med. 152, 211–217 (2010).

200.

Chilvers

CED

Knibb

Armstrong

Woods

Logan

RFA

: Postmenopausal hormone replacement therapy and risk of acute myocardial infarction - a case control study of women in the East Midlands, UK. Eur. Heart J. 24, 2197–2205 (2003).

201.

Weidemann

Hanke

: Cardiovascular effects of androgens. Cardiovasc. Drug Rev. 20, 175–198 (2002).

202.

Sieveking

Lim

Chow

RWY

: A sex-specific role for androgens in angiogenesis. J. Exp. Med. 207, 345–352 (2010).

203.

Wierman

Basson

Davis

: Androgen therapy in women: an Endocrine Society Clinical Practice guideline. J. Clin. Endocrinol. Metab. 91, 3697–3710 (2006).

204.

Blum

: Treating heart failure with sildenafil. Congest. Heart Fail. 15, 181–185 (2009).

205.

Kenny

Prestwood

Gruman

: Effects of transdermal testosterone on lipids and vascular reactivity in older men with low bioavailable testosterone levels. J. Gerontol. A Biol. Sci. Med. Sci. 57, 460–465 (2002).

206.

Sowers

Jannausch

Randolph

: Androgens are associated with hemostatic and inflammatory factors among women at the mid-life. J. Clin. Endocrinol. Metab. 90, 6064–6071 (2005).

207.

Ling

Komesaroff

Sudhir

: Cardiovascular physiology of androgens and androgen testosterone therapy in postmenopausal women. Endocr. Metab. Immune Disord. Drug Targets 9, 29–37 (2009).

208.

Marts

Keitt

: Foreward: A Historical Overview of Advocacy for Research in Sex-Based Biology. In: Principles of Sex-Based Differences in Physiology (34 Edition) Hay

Miller

(Eds). Elsevier Publishing Company (2004).

209.

Kim

Tingen

Woodruff

: Sex bias in trials and treatment must end. Nature 465, 688–689 (2010).

210.

Regitz-Zagrosek

Lehmkuhl

: Heart failure and its treatment in women. Role of hypertension, diabetes, and estrogen. Herz 30, 356–367 (2005).

211.

Lakoski

Greenland

Wong

: Coronary artery calcium scores and risk for cardiovascular events in women classified as “low risk” based on framingham risk score: the multi-ethnic study of atherosclerosis (MESA). Arch. Intern. Med. 167, 2437–2442 (2007).

212.

Miller

Black

Brinton

: Using basic science to design a clinical trial: baseline characteristics of women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS). J. Cardiovasc. Transl. Res. 2, 228–239 (2009).

213.

Comparison of the characteristics of women enrolled in the Kronos Early Estrogen Prevention study to those enrolled in the Women's Health Institute.

214.

Mulvagh

Behrenbeck

Lahr

: Endothelial function and cardiovascular risk stratification in menopausal women. Climacteric 13, 45–54 (2010).

215.

Shearman

Cooper

Kotwinski

: Estrogen receptor α gene variation is associated with risk of myocardial infarction in more than seven thousand men from five cohorts. Circ. Res. 98, 590–592 (2006).

216.

Shearman

Cooper

Kotwinski

: Estrogen receptor α gene variation and the risk of stroke. Stroke 36, 2281–2282 (2005).

217.

The Organization for the Study of Sex Differences www.ossdweb.org.

Sex-Based Differences in Vascular Function

Abstract

Keywords

Genetics of sex differences

Sex versus gender

Cardiovascular risk & Y chromosome

Cardiovascular risk & the X chromosome

Cardiovascular risk & the autosomes

Genetics of estrogen receptors

Genetics of steroid metabolism

Distribution of sex steroid receptors

Ligands & receptor activation

Sex steroids & vascular function

Sex steroids & prevention of cardiovascular disease

Future perspective

Footnotes

References