IDENTIFICATION OF GONADOTROPH ADENOMAS IN MEN WITH CLINICALLY NONFUNCTIONING ADENOMAS BY THE LUTEINIZING HORMONE-BETA SUBUNIT RESPONSE TO THYROTROPIN-RELEASING-HORMONE

Because of the recent finding that a majority of clinically nonfunctio ning pituitary macroadenomas in women could be identified as of gonado troph origin by their LH beta-subunit responses to TRH, we evaluated i n this study the value of the LH beta-subunit response to TRH in ident ifying gonadotroph adenomas in men with clinically nonfunctioning macr oadenomas. Thirty-eight consecutively studied men with clinically nonf unctioning macroadenomas were given TRH iv, and intact FSH and LH and LH beta- and alpha-subunits were measured every 15 min for 90 min befo re and 90 min after. TRH tests were also performed on 15 healthy, age- matched control men and on 12 men with adenomas secreting GH or PRL. O f the 38 men with clinically nonfunctioning macroadenomas, basal value s were supranormal in 10 for FSH and in 6 each for alpha- and LH beta- subunits. Responses to TRH were elevated, compared to the healthy, age -matched controls, in 14 for LH beta-subunit and in 5 each for intact FSH and LH. None of the men with adenomas secreting GH or PRL exhibite d supranormal responses to TRH. Of the 38 clinically nonfunctioning ad enomas, 35 were established in dispersed cell culture, and 29 secreted readily detectable amounts of intact FSH, LH, and LH beta-subunit, st rongly suggesting that these adenomas were of gonadotroph cell origin. We conclude that the LH beta-subunit response to TRH can identify gon adotroph adenomas in men with clinically nonfunctioning adenomas bette r than can basal concentrations of intact FSH and alpha-subunit, alone or combined, but not as well as it can in women.