Serum gonadotropin levels were determined in 10 patients with the amenorrhea-galactorrhea syndrome before and following acute iv administration of synthetic LH-releasing hormone (LHRH) or conjugated estrogens, in order to clarify the hypothalamic derangements in the gonadotropin secretion in patients with hyperprolactinemia. The basal prolactin (PRL) levels were elevated in all the patients, and blunted responses to 500 mug of iv synthetic thyrotropin-releasing hormone (TRH) injection were found in 9 out of the 10 patients. The basal levels of LH and FSH were subnormal in 2 and 3 patients, respectively, while those in the remaining patients were normal or slightly elevated. Normal or excessive responses of gonadotropins to 100 mug of iv LHRH were observed in most patients, 9 for LH and 10 for FSH out of 10 patients. In 10 normal cyclic women at the mid-follicular phase (D7-9) and 10 hypothalamic amenorrhea patients without galactorrhea, LH release was found 48 to 72 h after the iv injection of 20 mg conjugated estrogens (Premarin). This LH release following Premarin injection was completely abolished in the patients with amenorrhea-galactorrhea. These data seem to indicate that in patients with hyperprolactinemia, tonic secretion of gonadotropin is maintained fairly well, while of the positive feedback effect of Premarin on the release of LH is impaired. It is suggested that impaired LH release may be partly responsible for anovulation and amenorrhea in patients with hyperprolactinemia.

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