Androgens are the male sex hormones produced by the testes, ovaries, and adrenal cortex. They stimulate spermatogenesis, development of male secondary sex characteristics, and sexual maturity at puberty. Testosterone is the major endogenous androgen and is the prototype of the androgenic hormones. Androgens also have anabolic effects, which stimulate the formation and maintenance of muscular and skeletal protein. Athletes have used androgens to increase athletic performance, which has led to abuse of androgens. Androgens are considered controlled substances and are classified as Schedule III drugs. They have serious adverse effects such as hepatotoxicity, and their risks outweigh their benefits in increasing athletic performance.

Chemical derivatives of testosterone are known as anabolic steroids. They have a high anabolic activity.

Androgen inhibitors block the effect of endogenous androgens, inhibit the enzyme 5-alpha-reductase, and are called 5-alpha-reductase inhibitors. They are used to stop prostatic growth in benign prostatic hypertrophy (BPH).

Phosphodiesterase inhibitors enhance the effects of nitric oxide, a chemical that relaxes smooth muscle and increases blood flow to the penis during sexual stimulation.