When given in supraphysiological levels, anabolic/androgenic steroids commonly induce oligozoospermia. This is a form of reduced fertility characterized by having less than 20 million spermatozoa per ml of ejaculate. The quality of the sperm may also be impaired under the influence of AAS, as noted by an increase in the number of abnormal or hypokinetic (noticing reduced motion) sperm. Fertility is possible during oligozoospermia, however, as viable sperm are still made by the body. The odds of conception are just significantly lower than when sperm concentrations are normal. In many cases azoospermia is reached during AAS administration, which is defined as having no measurable sperm in the ejaculate. Conception is not possible with true steroid-induced azoospermia. Note that in some cases, fertility has been temporarily restored during active anabolic/androgenic steroid abuse with the use of human chorionic gonadotropin (HCG).
Diminished fertility is considered a reversible side effect of anabolic/androgenic steroid abuse. Sperm concentrations usually return to normal within several months of discontinuing drug intake. A substantial post-cycle recovery program based on the use of HCG, tamoxifen, and clomiphene may significantly shorten the refractory period, and is highly recommended among those in the steroid-using community. In a small percentage of cases, particularly following long periods of heavy steroid abuse, recovery of the HPTA can be very protracted, taking up to a year or longer for full recovery. Given the undesirable psychological and physical symptoms that can be associated with a prolonged state of low testosterone levels, such a long recovery window is rarely regarded as acceptable. This will usually prompt an individual to seek medical intervention or initiate an aggressive HPTA recovery program.
The ability of anabolic/androgenic steroids to suppress LH, FSH, and fertility has initiated a great deal of research surrounding their use as male contraceptives. Injectable testosterone has been extensively studied by the World Heath Organization, for example, and was determined to be a safe and moderately effective method of male birth control. In studies which administered 200 mg of testosterone enanthate per week to healthy men, azoospermia was achieved in 65% of patients within six months. Most of the remaining patients were oligozoospermic. This diminished fertility was fully reversible, and baseline sperm concentrations returned within seven months on average after drug discontinuance. A state of full azoospermia is the desired endpoint of male contraception, however, and this has not been reliably achieved with AAS drugs alone, even in high doses. Anabolic/androgenic steroids have, likewise, are not approved for use as male contraceptives.
Wlliam Llewellyn (2011) - Anabolics