The principal functions of male and female hormones are to control reproductive function and secondary sexual characteristics in their respective groups. Male hormones, such as testosterone, are usually referred to collectively as androgens. The female hormones consist of two principal groups: the estrogens (e.g., estradiol) and the progestins (e.g., progesterone). Androgens, estrogens, and progestins are classified as steroid hormones; their chemical structure is similar to those of the other primary steroid groups, the glucocorticoids and mineralocorticoids (see Chapter 29).
Male and female hormones are produced primarily in the gonads. Androgens are synthesized in the testes in the male. In the female, the ovaries are the main sites of estrogen and progestin production. As discussed in Chapter 29, small amounts of sex-related hormones are also produced in the adrenal cortex in both sexes, which accounts for the fact that low testosterone levels are seen in females, and males produce small quantities of estrogen. However, under normal conditions, the amounts of sex-related hormones produced by the adrenal cortex are usually too small to produce significant physiological effects.
In this chapter, we first discuss the physiological role of the male hormones and the pharmacological use of natural and synthetic androgens. We then address the physiological and pharmacological characteristics of the female hormones. Rehabilitation patients may use these agents for approved purposes, such as female hormones as contraceptives. These agents may also be used for illicit reasons, such as the use of male hormones to enhance athletic performance. Hence, you should be aware of the therapeutic and potential toxic effects of these drugs.
Source and Regulation of Androgen Synthesis
In adult males, testosterone is the principal androgen produced by the testes.1,2 Testosterone is synthesized by Leydig cells located in the interstitial space between the seminiferous tubules (Fig. 30-1). The seminiferous tubules are the convoluted ducts within the testes in which sperm production (spermatogenesis) takes place. Testosterone produced by the Leydig cells exerts a direct effect on the seminiferous tubules, as well as systemic effects on other physiological systems (see “Physiological Effects of Androgens”).
Effects of pituitary gonadotropins on spermatogenesis. Luteinizing hormone (LH) stimulates testosterone (T) production from Leydig cells. Follicle-stimulating hormone (FSH) acts primarily on Sertoli cells to increase synthesis of androgen-binding protein (ABP). ABP appears to bind with T and facilitate transport into the seminiferous tubule, where spermatogenesis takes place.
Production of testosterone by the Leydig cells is regulated by the pituitary gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH).1 LH and FSH appear to control spermatogenesis, as shown in Figure 30-1. LH is the primary hormone that stimulates testosterone production. LH released from the anterior pituitary binds to receptors on the surface of Leydig cells and directly ...