RATES OF TESTOSTERONE-INDUCED SUPPRESSION TO SEVERE OLIGOZOOSPERMIA OR AZOOSPERMIA IN 2 MULTINATIONAL CLINICAL-STUDIES

Two multicentre studies of the contraceptive efficacy of azoospermia a nd severe oligozoospermia were conducted in 16 centres in 10 countries . They used a common protocol of weekly testosterone injections for sp erm suppression, the patterns and degrees of which were compared among men from different population groups. Six hundred and seventy normal, healthy volunteers, of whom 205 were Asian (mostly Chinese) and 465 o f non-Asian origin, were given weekly injections of testosterone enant hate, 200 mg IM, during the suppression (6-month) and efficacy (12-mon th) phases. Patterns of sperm suppression were assessed by semen analy sis at monthly or 2-weekly intervals. Sperm counts suppressed more slo wly in the Asian than in the non-asian men in the first 2 months of in jections but subsequently suppressed to lower sperm concentrations by 6 months. The cumulative life table rates of suppression to sperm conc entrations below 5 million/ml, 3 million/ml or azoospermia at 6 months were 97.1%, 95.6%, and 66.7%, respectively for non-asian men, compare d to 99.4%, 98.4% and 89.2%, respectively for Asian men. In conclusion , a hormonal contraceptive method based on regular testosterone inject ions can suppress spermatogenesis to azoospermia or severe oligozoospe rmia in 97% of men, regardless of their ethnic origin.