Atrophy of gonadotrophin producing cells Exogenously LH synthesis administered androgens and release or anabolic steroids are decreased Prostate Testes Normal function. Testosterone synthesis in The deficit of endogenously Leydig cells is decreased. The synthesized testosterone is exogenously administered compensated for by the steroid is not able to exogenously administered compensate for the deficit of steroid endogenously synthesized testosterone Figure 2 Intratesticular and serum testosterone concentrations after treatment with andro gens or anabolic steroids in order to substitute for the peripheral androgen deficiency and to achieve azoospermia. Because this steroid is alkylated in position 17, toxic effects on liver function can not be excluded. Danazol offers no advantages as compared with other anabolic steroids; rather, disadvantages. Numerous experiments of this type have been performed during the last 40 or 50 years. The outcome in each case was more or less identical: with a certain dose of an androgen or anabolic steroid it is possible to inhibit spermatogenesis without interfering with other androgen-dependent func tions, including libido (potentia coeundi) and accessory sexual glands. On the basis of this pharmacological-endocrinological background, androgens and anabolic steroids can be used for male fertility control, and several clinical trials have been performed during the last 10-15 years. Some of 1 these studies 2-23 are mentioned in Table 2.