They are used illegally by some athletes in hopes of increasing muscle mass and improving performance.
Weight gain does occur, including swelling due to fluid accumulation.
Steroids are taken orally or injected. Sharing of needles has resulted in the spread of the AIDS virus. Steroid use can become addictive. Adolescents may experience accelerated bone maturation, stunting their growth. Women experience signs of masculinization, including increased body and facial hair.