Effect of short-term cyclic administration of cyproterone acetate on pituitary-ovarian function in the human

Short courses of cyproterone acetate, a compound with progestational and antiandrogenic activities, were administered to normally menstruating women during different phases of the menstrual cycle to suppress growth and maturation of the follicles and corpus luteum function. Postovulatory administration of 20 mg of the drug daily for 8 days to two women delayed menstruation by 4 to 6 days, followed by prolonged bleeding and short post-treatment cycles. Plasma levels of progesterone were suppressed temporarily during therapy, but increased immediately after cessation of treatment. Administration of 10 mg of the drug for 8 days during the early follicular phase to two women resulted in irregular bleeding, short cycles, and decreased plasma levels of progesterone throughout the cycle. Reduction of the dose to 2.5 mg during the early follicular phase in two other women also resulted in irregular cycles. When the 2.5-mg dose was administered to three women from the 8th to the 15th days of the cycle, vaginal bleeding and cycle length were normal. Plasma levels of luteinizing hormone and progesterone were suppressed during therapy. In one subject, cervical mucus was found to be hostile to sperm penetration in all three treatment cycles. The results indicate that, with cyclic administration of low doses of cyproterone acetate to women during the late follicular phase, it may be possible to interrupt pituitary-ovarian function, as well as sperm transport through the cervical mucus.