Effects of testosterone enanthate in normal men: experience from a multicenter contraceptive efficacy study. World Health Organization Task Force on Methods for the Regulation of Male Fertility.

OBJECTIVE

To evaluate the secondary impact of a prototype androgen contraceptive regimen on physical, metabolic and behavioral variables.

DESIGN

Prospective, open, noncomparative contraceptive efficacy study.

SETTING

International multicenter study comprising 10 centers in seven countries.

SUBJECTS

Two hundred seventy-one healthy men, age 31.8 +/- 5.4 years (mean +/- SD), range 21 to 45 years.

INTERVENTIONS

Weekly IM injections of 200 mg T enanthate.

MAIN OUTCOME MEASURES

Adverse effects and discontinuations; biochemical and hematologic changes and interpopulation differences.

RESULTS

Chinese subjects were shorter and lighter and their baseline hemoglobin, plasma lipid, and liver enzyme levels were lower than in non-Chinese subjects. The most common side effects were painful injections, acne, fatigue, and weight gain. Gynecomastia and prostate problems were detected in 24 and 9 men, respectively, though no men stopped injections for such reasons. Testosterone enanthate increased body weight, hemoglobin, and urea but decreased testicular volume and creatinine. Plasma triglyceride, cholesterol, and low-density lipoprotein cholesterol were unchanged; high-density lipoprotein cholesterol decreased by 14% to 18% in non-Chinese but was unchanged in Chinese men. Liver transaminases were increased by 36% to 51% in Chinese but were unchanged in non-Chinese subjects. These T enanthate-induced effects were reversible within 6 months of stopping injections and were not related to the duration of T exposure.

CONCLUSIONS

Testosterone enanthate administration in a contraceptive trial produced significant but reversible effects on skin, muscle, liver, lipid metabolism, and hemopoietic functions that varied between population groups. These effects reflect the relatively high peak levels and fluctuations of plasma T produced by the weekly T enanthate regimen rather than an inherent feature of hormonal male contraception. The results highlight the need for long-acting preparations of T with more stable delivery kinetics.