Male fertility regulation with cyproterone acetate (CPA).
The objectives of this investigation were to analyze the effects of medium dose cyproterone acetate, for short cyproterone acetate (CPA), on spermatogenesis, seminal plasma content, sperm migration, and serum gonadotropins and androgens. The study was primarily designed to test the hypothesis proposed by Prasad from India on the basis of data accumulated in the rat model that CPA in small doses selectively inhibits sperm maturation in the epididymis, thus resulting in temporary infertility without actually suppressing testicular function. 30 healthy male volunteers of either presumed or proven fertility, according to the guidelines of the Andrology Club, aged 21-38 years, participated in the study. After a control period of 12-18 weeks, the volunteers received 10-20 mg of CPA daily for 12-26 weeks followed by a 2nd control period of 12-16 weeks. After 4 weeks of treatment, the sperm count had decreased to levels generally accepted as being "subfertile." The proportion of normal spermatozoa decreased in parallel fashion. The proportion of pathological, immature, and dead cells increased at the same time. During CPA treatment, the percentage of motile spermatozoa was significantly reduced when measured 30 minutes as well as 4 hours after ejaculation. The qualitative assessment of sperm motility showed a distinct reduction in speed. After 4 weeks of CPA medication a distinct reduction was observed in the distance traveled by the spermatozoa through capillary tubes containing human cervical mucus of ovulation quality. There was a significant decrease of the so-called sperm migration index in all cases to values presumably not any longer compatible with fertility. In vivo sperm recovery tests showed that the administration of 10 mg of CPA daily to males whose wives had previously undergone tubal ligation showed that sperm migration at midcycle was arrested at the cervical level. The data indicate the importance of multiple serial determinations to compensate for the random fluctuations of peripheral gonadotropins. On an average luteinizing hormone (LH) concentrations were about 35% lower during CPA administration, which was statistically significant. The episodic variations, which normally occur every 90-180 minutes, continued during the treatment phase. Basal LH returned to pretreatment control levels within 4 weeks after cessation of CPA. Similar observations were made for follicle stimulating hormone (FSH). Basal serum testosterone was suppressed by 70%.