Background: Pituitary adenomas that arise from the gonadotroph cells are being recognized with increasing frequency in men, but they are still rarely recognized in women. This rarity could be the result of an actual difference in occurrence or of greater difficulty in recognition. The tumors are usually recognized in men more than 50 years old, but elevated serum gonadotropin levels in women of that age could be produced by normal gonadotroph cells.
Methods: Because the stimulation of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and the beta subunit of LH (LH beta) by thyrotropin-releasing hormone (TRH) is a characteristic of gonadotroph adenomas in men, we administered TRH to 16 women with apparently nonsecreting pituitary macroadenomas and measured serum FSH, LH, LH beta, and the glycoprotein hormone alpha subunit every 15 minutes for 90 minutes before and 90 minutes after. The results were compared with the responses in 16 healthy women matched for age and in 10 women with macroadenomas secreting prolactin, growth hormone, or corticotropin. The tumors from 12 of the women with nonsecreting adenomas were cultured, and the secretion of FSH, LH, and LH beta in culture was determined.
Results: Eleven of the 16 women with apparently nonsecreting adenomas had significant increases in serum LH beta in response to TRH, 3 had FSH responses, and 4 had LH responses. None of the 16 healthy women and none of the 10 women with secreting macroadenomas had LH beta, FSH, or LH responses to TRH. Ten of the 12 adenomas that were cultured secreted readily detectable amounts of FSH, LH, and LH beta, and their secretion in vitro correlated with the patients' responses to TRH in vivo.
Conclusions: Most apparently nonsecreting pituitary macroadenomas in women arise from gonadotroph cells. The majority of these can be recognized, even in postmenopausal women, by the serum LH beta responses to TRH, and some can be recognized by the responses of serum FSH and LH.