Anabolic steroids attract young people and adults, who take these drugs to enhance athletic performance and improve their body image. Even though they may take these steroids with good intentions, they may not understand that the drugs are potentially harmful. These problems include aggressive behavior, liver disease, and increased risk of heart disease and certain cancers. Anabolic steroids also can cause permanent undesirable changes in sex characteristics, such as breast growth in men and increased facial hair and deepened voice in women. Among youth who have not attained their natural height, anabolic steroids can stunt their growth. Anabolic steroids should never be taken except while under a doctor's care.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine .