Steroids are any one of a large number of compounds that are related to sterols. Steroids include bile acids, D vitamins, certain hormones, and certain carcinogenic substances. Sterols are alcohols with a cyclic nucleus. An example of a steroid is cholesterol. In the human organism, cholesterol is the parent compound of all steroid hormones.

The accompanying illustration shows some of the most important steroid hormones. Their similarity to cholesterol is obvious. In the adrenal glands located above the kidneys, the synthesis of hydrocortisone, aldosterone, and a portion of the body's testosterone are produced. All human females produce a small amount of testosterone in this manner. It is the testes of males, however, that synthesize the greatest quantity of testosterone and account for male secondary sexual characteristics (e.g. facial hair, deep voice, etc.) In the ovaries of the female, estrogens and other female hormones are produced. Estradiol is...