Steroids

Abstract

The steroids are a group of compounds containing a four-ring structure termed the cyclopentanoperhydrophenanthrene nucleus (Fig. 1). As shown in Fig. lb, the nucleus itself is composed of 17 carbon atoms; however, the synthesis of the steroid hormones involves the addition of one, two, or four additional carbon atoms to form the CI8 estranes, C19 androstanes, and C21 pregnanes, respectively (Fig. 2). The CI8 steroids include estradiol, estrone, and estriol. Estradiol is synthesized mainly in the ovary, with transformation to estrone and estriol taking place in the liver. Some synthesis also occurs in the adrenal as well as in the testis. Testosterone and dihydrotestosterone are examples of the C19 steroids. The major synthesis of testosterone occurs in the testis; however, androgen production has also been shown to occur in the adrenal and the ovary. The C21 steroids are produced mainly in the adrenal gland and include progesterone (also synthesized by the ovary), the glucocorticoids such as Cortisol, and the mineralocorticoids such as aldosterone.