Changes in the prolactin response to thyrotropin-releasing hormone (TRH) throughout the proliferative phases in the ovulatory and anovulatory menstrual cycle.

This study was undertaken to determine the changes of prolactin (PRL) response to thyrotropin-releasing hormone (TRH) throughout the menstrual cycle. The infertile patients with normal ovulatory menstrual cycle and with normoprolactinemic anovulatory cycles were assigned to intravenous loading tests with TRH (0.5 mg) and gonadotropin-releasing hormone (Gn-RH)(0.1 mg) during the proliferative phase of the cycle. In normal ovulatory patients, the basal PRL and gonadotropin levels did not significantly vary, while the response to TRH was reduced to late proliferative phase, compared to early and mid-phases. The response of luteinizing hormone (LH), but not follicle-stimulating hormone (FSH) was approximately 2-fold higher in the late proliferative phase than in early or mid-phases. In patients with normal PRL and high LH (over 8 mIU/ml), both basal levels and responses to Gn-RH of the gonadotropins were higher than those in the normal ovulatory cycle, but PRL profiles was essentially equal to those in the late proliferative phase of normal cycle. No significant differences of basal and stimulated levels of gonadotropins and PRL were observed in patients with normal PRL and LH levels. Thus PRL response rather than basal level may be related to gonadotropin secretion and consequently menstrual cycle.