Performance enhancing substances For Body Building

Some bodybuilders use drugs to gain an advantage in hypertrophy, especially in professional competitions. Although these substances are illegal without prescription in many countries, in professional bodybuilding anabolic steroids and precursor substances such as prohormones are used very frequently. Anabolic steroids cause muscle hypertrophy of both types (I and II) of muscle fibers caused likely by an increased synthesis of muscle proteins. Some negative side-effects accompany steroid abuse, such as hepatotoxicity, gynecomastia, acne, male pattern baldness and a decline in the body's own testosterone production, which can cause testicular atrophy.^[22][23][24]

Growth Hormone (GH) and insulin are also used. GH is relatively expensive compared to steroids, while insulin is very readily available yet fatal if misused. See Growth hormone treatment for bodybuilding.