Androgenic steroids are hormones that increase muscle power and a competitive, aggressive drive. In females these substances may cause masculinization of personality, voice, and genitals as well as increases in energy and libido. In males the body reduces its own supply of androgens to compensate for those from the outside. This can lead to genital atrophy, breast development, and infertility. (Wilson, Glenn. The Great Sex Divide. p 121-122. England: Peter Owen Publishers, 1989.)