Exaggerated prolactin response of thyrotropin-releasing hormone in women with anovulatory cycles: possible role of endogenous estrogens and effect of bromocriptine.

Twenty-one women 18 to 36 years old, presenting with chronic anovulation, were compared with 10 normally cycling women. The patients were characterized by low progesterone (P) levels (0.93 +/- 0.14 ng/ml versus 15.5 +/- 1.4 in controls), whereas 17 beta-estradiol (E2) was moderately decreased (110.2 +/- 8.3 pg/ml versus 162.8 +/- 14.5 in controls) realizing a relative hyperestrogenism. Basal prolactin (PRL) levels were not elevated (12.1 +/- 0.97 ng/ml versus 9.2 +/- 0.7 in controls), but after thyrotropin-releasing hormone (TRH) stimulation an exaggerated response was observed (114.5 +/- 7 ng/ml versus 55.8 +/- 9 in controls). Patients were treated with bromocriptine (1.25 mg 2 times a day) for 3 months. Fifteen responded with ovulatory cycles, and five became pregnant. Progesterone increased significantly (10.2 +/- 1.3 ng/ml), whereas in patients who did not ovulate P increased only slightly (1.56 +/- 0.18 ng/ml). The particular endocrine profile of these patients (P/E2 imbalance) realizing relative hyperestrogenism may be responsible for the exaggerated PRL response to TRH. Bromocriptine, in reducing this transient, or masked, hyperprolactinemia, allows in many patients the return to ovulatory cycles. This mechanism may be one of the possible pathways leading to chronic functional or organic hyperprolactinemia.