Testosterone Injections Suppress Sperm Production, Providing Effective Level of Contraceptive Protection

Abstract

399 healthy men aged 21-45 participated in a clinical trial of weekly injections of testosterone enanthate at 15 research centers in nine countries in Asia Europe Australia and the US. During the period between initial injection and achievement of azoospermia or oligozoospermia on three consecutive semen assays the female partners used contraception. Even though men in the Asian centers achieved oligozoospermia later than those at the other centers (median 77 vs. 57 days; p = .003) they achieved azoospermia more quickly (median 91 vs. 112 days p < .001). 98% of the men in the efficacy phase of the study achieved azoospermia and 77% of them remained azoospermic throughout the trial. The overall pregnancy rate was 1.4/100 person-years. The pregnancy rate among azoospermic men was 0% 5.1% for men with sperm concentrations in the range of 0.1-1 million/ml 14.5% for men with concentrations of 1.1-2 million/ml and 28.3% for men with concentrations of 2.1-3 million/ml. At follow-up 64% of men had a normal sperm concentration (median time to recovery = 112 days). 34% returned to their baseline concentration (median time to recovery = 203 days). The relatively long period required for the onset of effective sperm suppression and for recovery of sperm production is a major limitation of the testosterone enanthate injection. The annual life-table discontinuation rate was 33% (12% for personal reasons). 5% withdrew due to difficulties with the injection. About 5% discontinued the injections due to side effects the most common of which were acne (80 men) abnormal breast tissue (24) and fatigue (22).