A performance-enhancing drug is any substance taken by athletes to improve performance. In sports, the phrase performance-enhancing drugs are popularly used in reference to anabolic steroids or their precursors. Some athletes take a form of steroids known as anabolic androgen steroids or just anabolic steroids to increase their muscle mass and strength. Some athletes take straight testosterone to boost their performance. Taking anabolic-androgenic steroids to enhance athletic performance, besides being prohibited by most sports organizations, is illegal. Some physiological and psychological side effects of anabolic steroid abuse have potential to impact any user, while other side effects are gender specific. Physiological: Acne, Male pattern baldness, Liver Damage, Stunted growth and disruption of puberty in children. Psychological: Increased aggressiveness and sexual appetite.