THE EFFECT OF THYROTROPIN-RELEASING-HORMONE ON GONADOTROPIN AND FREE ALPHA-SUBUNIT SECRETION IN PATIENTS WITH ACROMEGALY AND FUNCTIONLESS PITUITARY-TUMORS

Paradoxical response of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and alpha-subunits (alpha-SU) to thyrotropin-releasing hormone (TRH) have previously been reported in individuals with clini cally nonfunctioning pituitary tumors (NFT). In the present study, we assessed the in vivo responses of LH, FSH, alpha-SU to TRH in 34 patie nts with NFT and 29 patients with agromegaly. Twenty-three clinically NFT were postoperatively analyzed by immunocytochemistry and 21 staine d positive for beta-FSH and/or beta-LH. Two patients with NFT had elev ated basal circulating levels of FSH (41.5 IU/L) and thus were charact erized as FSH-secreting adenomas. TRH in these patients increased LH f rom basal 1.6 IU/L to 32.6 IU/L. In other patients with NFT, circulati ng levels of glycoprotein peptides were not elevated. TRH induced sign ificant rise of LH in 8 (23.5%), FSH in 5 (14.7%), and alpha-SU in 10 (29.4%) patients with NFT. Thus, a bolus dose of TRH elicited a notabl e increment in FSH, LH or alpha-SU in 23 of 34 patients with NFT. Amon g 29 patients with acromegaly, LH rose in 6 (20.7%), FSH in 5 (17.2%), and alpha-SU in 3 (10.3%) patients. In conclusion: (1) We confirm tha t most NFTs are capable of synthesizing gonadotropin hormones and subu nits (beta-FSH, beta-LH). (2) Most patients in our study responded by either FSH, LH or alpha-SU secretion after TRH, independent of basal h ormone levels. Furthermore, recent studies show that by measurement of TRH stimulated beta-FSH and beta-LH one might further improve the dia gnostic tools. (3) Gonadotropin response and possibly alpha-SU to TRH are also found in some patients with acromegaly. This could be a marke r of a plurihormonal pituitary tumor.