Factors in nonuniform induction of azoospermia by testosterone enanthate in normal men. World Health Organization Task Force on Methods for the Regulation of Male Fertility.

OBJECTIVE

To identify factors differentiating men becoming azoospermic from those remaining oligozoospermic within 6 months of T treatment.

DESIGN

Prospective, open, noncomparative contraceptive efficacy study.

SETTING

International multicenter study of 271 men in 10 centers in seven countries.

PATIENTS

Data from 157 achieving azoospermia and 68 remaining oligozoospermic after 6 months of treatment were analyzed. The remaining 46 men were excluded as having unclassifiable suppression status due to discontinuation before completion of suppression.

INTERVENTIONS

Weekly IM injections of 200 mg T enanthate.

MAIN OUTCOME MEASURES

Anthropometric, seminal, hormonal, and biochemical data obtained before, during, and after treatment as potential predictors of consistent azoospermia.

RESULTS

Azoospermic men had [1] faster rates of fall in sperm output and, after a delay of 75 +/- 4 days (mean +/- SE) for sperm to reappear in the ejaculate, exhibited a faster rate of recovery of sperm output; [2] higher pretreatment levels of FSH (mean +/- SE; 3.7 +/- 0.3 versus 2.7 +/- 0.4 mIU/mL [conversion factor to SI units, 1.00]); and [3] (if treated for > 15 months) a prolonged after treatment rebound in gonadotropins compared with nonazoospermic men. There were no other differences in pretreatment variables or plasma T levels and changes in androgen-sensitive markers during treatment. None of the variables explained the higher rates of azoospermia among men in Chinese (91%, n = 3) compared with non-Chinese centers (60%, n = 7).

CONCLUSION

Nonuniformity of T-induced azoospermia among healthy fertile men is not due to anthropometric or ethnic differences, to variations in androgen effects, or to poor compliance with treatment. The heterogeneity in individual susceptibility to T-induced azoospermia is most consistent with quantitative differences in the hormonal regulation of spermatogenesis and is likely to be evident with other hormonal methods for male contraception.