We describe two case histories that highlight some of the endocrine effects of doping with androgenic anabolic steroids. The main endocrine effect observed after use of androgenic anabolic steroids is the development of hypogonadotrope hypogonadism, characterized by low levels of gonadotrophins, suppression of testosterone production and azoospermia. If testosterone is used alone, or in combination with synthetic anabolic steroids, the circulating levels of testosterone are normal or high. Oestrogen levels may be elevated owing to aromatization of testosterone. The level of sex hormone binding globulin is suppressed. These endocrine parameters are of practical use in evaluating patients misusing androgenic anabolic steroids.