Abstract
Just as practitioners at the interface of organic medicine and psychiatry strive to define their roles, so does this book. Part of the Progress in Psychiatry series, this book deals with the physiology, molecular biology, clinical and public health aspects of thyroid disease. While not claiming to be a comprehensive review of thyroid disease, it demands attention from a wide audience. However, individual readers may find the diverse contents of the chapters intimidating, and the contents of the final one somewhat surprising.
Part One (Chapters 1 and 2) is extremely detailed and recommended reading for candidates of the Australasian College of Physicians written examination. Chapter 1 reviews thyroid physiology, function and disease, especially in pregnancy, fetal ontogeny and the abrupt changes in the perinatal period. Controversies such as the relative contribution of transplacental hormones to the fetus, measurement of hormone levels in newborns and routine thyroid supplementation of premature infants are discussed.
Chapter 2 extends understanding of thyroid hormone physiology to the molecular level. The effects of thyroid hormone on developing neurones in vivo and on the fetal brain are described and diagrams help elucidate receptor form, function and post-receptor nuclear activation. The clinical relevance of these complex interactions is illustrated by the condition of resistance to thyroid hormone (RTH).
The clinical section (Chapters 3–8) of the book starts with an overview of newborn screening for congenital hypothyroidism (CH), including an interesting historical insight. This is an important chapter for it places much of current practice of early detection, treatment and follow-up of thyroid disease in children into perspective. While current practice avoids catastrophic outcomes, children treated for CH have selective impairments including language delays, minor motor problems, visual-spatial deficits and problems with attention. Severe and early (possibly in utero) CH appears to be important, but ongoing vigilant monitoring and treatment is required.
A chapter is devoted to RTH, an uncommon condition in which thyroid receptor insensitivity leads to elevated levels of both thyroid hormone (TH) and thyroid stimulating hormone (TSH). The rate of attention deficit hyperactivity disorder (ADHD) in children with RTH has been reported to be as high as 70%. Hauser proposes using RTH as a model for ADHD, allowing prospective study of behaviour, attention, language and motor development, notwithstanding some subtle differences in the two subsets upon psychological testing.
The dilemmas of how to manage children with thyroid disease and developmental delay, learning difficulties or ADHD are given scant regard. For example, it remains unclear whether there is role for TH manipulation in managing behaviour associated with RTH. Paediatricians or child psychiatrists searching for effective or innovative ways of managing such children may be disappointed.
The cognitive and behavioural abnormalities associated with acquired juvenile hypothyroidism and thyrotoxicosis occupy Chapters 6 and 7. The presentation of children with hypothyroidism is often unremarkable, sometimes only with poor school performance. However, more often than not, cognition and behaviour are normal upon diagnosis and deteriorate as euthyroidism is achieved. Several case studies as well as prospective studies are presented to support this observation. An untested approach, to start with low doses of thyroxine and gradually increase it to the minimum required to suppress TSH, is advocated, at least in older children. Stimulant medication and beta-blockers may have a role.
Conversely, thyrotoxicosis may result in many behavioural, neurological, cognitive and psychiatric problems, such as ADHD symptoms, anxiety, mood disorders and psychosis. Children with thyrotoxicosis seem to particularly have problems with shifting attention from task to task. Early diagnosis and accurate assessment of deficits were felt to be important in forming a sound management and educational plan.
The final chapter of the book is a conundrum. Bhatara, McMillin and Hauser introduce the spectre of synthetic ‘thyroid disrupting contaminants’ (TDCs), such as dioxin. Thyroid disrupting contaminants have been linked to human disease in well-known cases such as the 1968 Yusho incident in Japan, in which ingestion of contaminated cooking oil left affected infants with severe developmental delay. Laboratory animal studies have demonstrated TDCs to be neurotoxins that preferentially affect developing young animals via TH receptors. The data on chronic, environmental-level exposure of infants and children to TDCs, however, are contradictory. Attention, cognition and memory problems found in the original study were not supported by a larger prospective study, and a third small study is open to interpretation.
On the one hand, the authors ought to be praised for alerting professionals to a potential worldwide health risk for infants and children. Initial reports of new environmental hazards are often greeted with scepticism or apathy, and certainly, more research on the effects of environmental TDCs in humans is required. However, the choice of references and interpretation of data in the final chapter was less than sound, especially in comparison with the preceding chapters. Furthermore, many of the arguments and conclusions drawn, particularly on the urgent need to act on TDCs, were unsupported and less than compelling.
Overall, the book contains a wealth of information and references. Each section of the book has its audience: postgraduate examination candidates, obstetricians, neonatologists, paediatricians, child psychiatrists, allied health professionals, researchers, public health advocates among others. However, there appears to be little overlap between what each professional group may find useful, and there is also a fair degree of repetition between chapters. To these ends, a problem-oriented approach may have served the book better.