AS are derivatives of testosterone, which has strong genitotropic effects. For this reason, it will not be surprising that side effects include the reproductive system. Application of anabolic steroids leads to supra-physiological concentrations of testosterone or testosterone derivatives. Via the feed back loop, the production and release of luteinizing hormone (LH) and follicle stimulation hormone (FSH) is decreased.
Prolonged use of anabolic steroids in relatively high doses will lead to hypogonadotrophic hypogonadism, with decreased serum concentrations of LH, FSH, and testosterone.
There are strong indications that the duration, dosage, and chemical structure of the anabolic steroids are important for the serum concentrations of gonadotropins. A moderate decrease of gonadotropin secretion causes atrophy of the testes, as well as a decrease of sperm cell production. Oligo, azoospermia and an increased number of abnormal sperm cells have been reported in athletes using AS, resulting in a decreased fertility. After stopping AS use, the gonadal functions will restore within some months. There are indications, however, that it may take several months.
In bodybuilding, where usually high dosages are uses, after stopping steroid use, often choriogonadotropins are administered to stimulate testicular function. The effectiveness of this therapy is unknown.