Role of androgens in the regulation of the human menstrual cycle.

Although previous investigations have examined the importance of androgens in the regulation of the human menstrual cycle, no consensus has been reached, due to conflicting results. We have therefore used the non-steroidal anti-androgen flutamide as a pharmacological probe to evaluate the role of androgens in the control of gonadotropin secretion in normally cycling women. Eight women were studied during control and treatment cycles, during which either placebo (as control) or flutamide (750 mg orally) was given daily. Blood was sampled every other day during the follicular and luteal phases and daily around the expected midcycles for determination of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, progesterone and androgens (testosterone, androstenedione, dehydroepiandrosterone sulfate) by radioimmunoassay and immunoradiometric assay. To establish unstimulated and gonadotropin releasing hormone (GnRH)-stimulated gonadotropin profiles, blood samples were frequently collected (every 10 min for 8 h, GnRH 25 micrograms i.v. after 7 h on day 10 in both the control and treatment cycles. Compared to control conditions, the durations of both the follicular and luteal phases did not change considerably during flutamide treatments. Serum androgen levels (testosterone, androstenedione, dehydroepiandrosterone sulfate) were significantly (p < 0.01) reduced during androgen antagonism. Daily gonadotropin and estradiol levels did not differ between control and flutamide cycles, while progesterone secretion tended to be attenuated (p = 0.2) during the luteal phases of the flutamide cycles. The LH and FSH secretory profiles and the GnRH-stimulated gonadotropin responses remained virtually unchanged during androgen antagonism.(ABSTRACT TRUNCATED AT 250 WORDS)