Abstract
Paradoxical response of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and α-subunits (α-SU) to thyrotropin-releasing hormone (TRH) have previously been reported in individuals with clinically nonfunctioning pituitary tumors (NFT). In the present study, we assessed the in vivo responses of LH, FSH, α-SU to TRH in 34 patients with NFT and 29 patients with agromegaly. Twenty-three clinically NFT were postoperatively analyzed by immunocytochemistry and 21 stained positive for β-FSH and/or β-LH. Two patients with NFT had elevated basal circulating levels of FSH (41.5 IU/L) and thus were characterized as FSH-secreting adenomas. TRH in these patients increased LH from basal 1.6 IU/L to 32.6 IU/L. In other patients with NFT, circulating levels of glycoprotein peptides were not elevated. TRH induced significant rise of LH in 8 (23.5%), FSH in 5 (14.7%), and α-SU in 10 (29.4%) patients with NFT. Thus, a bolus dose of TRH elicited a notable increment in FSH, LH or α-SU in 23 of 34 patients with NFT. Among 29 patients with acromegaly, LH rose in 6 (20.7%), FSH in 5 (17.2%), and α-SU in 3 (10.3%) patients. In conclusion: (1) We confirm that most NFTs are capable of synthesizing gonadotropin hormones and subunits (β-FSH, β-LH). (2) Most patients in our study responded by either FSH, LH or α-SU secretion after TRH, independent of basal hormone levels. Furthermore, recent studies show that by measurement of TRH stimulated β-FSH and β-LH one might further improve the diagnostic tools. (3) Gonadotropin response and possibly α-SU to TRH are also found in some patients with acromegaly. This could be a marker of a plurihormonal pituitary tumor.
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