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 . 
Side-effects from the use of steroids are extremely common and can be quite significant. Most side-effects are reversible once the athlete stops usage although serious long-term side-effects and even death have occurred as a direct result of steroid use.
• Decreased sperm production and sex drive
• Increased aggression, irritability and mood swings
• Liver disorders
• Baldness (alopecia)
• Hypertension (high blood pressure)
• Raised cholesterol
• Gynecomastia (development of over-sized mammary glands in males)
• Menstrual irregularities (in women)
• Hirsuitism (excessive hair growth occurring in females which follows the pattern of male hair growth, . facial)
• Deepening of the voice
• Reduced immunity
• Possible development of tumors (wilm’s tumor, prostate carcinoma and leukemia have been reported, although a connection is not proven)
Not shortly after Roger Maris record was broken, another baseball player, Jason Giambi and various other athletes were either suspected of, or proven to have, taken anabolic steroids. Again, Congress convened a hearing, and just as they did the first time in 1990, they did not determine that steroids were a danger, but rather that the danger was more in protecting professional sports organizations. The updated statute has been updated to proscribe pro-hormones also The definition of an anabolic steroid as defined currently in the United States under (41)(A) is that "anabolic steroid" means any drug or hormonal substance, chemically and pharmacologically related to testosterone (other than estrogens , progestins, corticosteroids, and dehydroepiandrosterone (7).