The effects of low doses of cyproterone acetate on some functions of the reproductive system in normal men.

One daily dose of either 5 mg or 10 mg cyproterone acetate (CA) was administered to 2 groups of 4 fertile men for 6 months. The medication was preceded by a 3 months placebo period and followed by a recovery phase of 5 to 8 months. During CA-treatment the sperm count/ml decreased and the percentage of abnormal spermatozoa increased slightly (0.991 less than P less than 0.05). Sperm penetration assessed by the Kremer test did not show any decrease during treatment. Serum levels of testosterone and FSH decreased, but those of LH remained unchanged during treatment. Two pregnancies occurred after 13/4 and 51/2 months of CA-treatment. The serum-CA concentration in these 2 volonteers did not differ from that of the remainder. Three subjects who began the study were withdrawn because of depressive mood changes (2) and weakness combined with dizziness (1). Data from these subjects were not included. The results indicate that daily doses of 5 mg and 10 mg of cyproterone acetate are not effective as a male contraceptive.