The five major classes of steroid hormones.

Estrogens, androgens, progestogens, glucocorticoids, and mineralocorticoids are usually divided into three main groups according to the number of carbon atoms they possess. For this discussion they are divided into four groups. Pregnane steroids have 21 carbon atoms and include progesterone, glucocorticoids, and mineralocorticoids. Androstane steroids have 19 carbon atoms and include testosterone and other related androgens. Estrane steroids have 18 carbon atoms and include estradiol and many of the 19 nortestosterone derivatives used as progestogens in oral contraceptives that have an ethinyl group at position 17 alpha, and the absence of a methyl group between the A and B rings. The more biologically active gonane steroids possess the structure of the estrane steroids and additionally have an ethyl group at position 13, and a keto group at position 3.

C. Matthew Peterson, M.D. Progestogens, Progesterone antagonists, progesterone, and androgens: synthesis, classification and uses. Clinical Obstetrics and Gynecology, 1995; 38: 813-20.

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