Biochemistry, Vol. 3 - A. Lehninger 1985

Selected Aspects of Human Biochemistry
Hormones
Sex hormones are steroids

Like the Hormones of the adrenal cortex, androgens (Male Sex Hormones) and estrogens (Female Sex Hormones) are Steroids. The adrenal cortex, Testes, and Ovaries share a common embryological origin, but this is not their only point of similarity. For instance, androgens are synthesized not only in the testes, but also (albeit in smaller quantities) in the adrenal cortex and ovaries. Similarly, estrogens are produced not only in the ovaries, but also in the adrenal cortex and testes. Essentially, sexual characteristics are determined by The ratio of secreted androgens to estrogens. Ultimately, all Steroid Hormones are derived from a common precursor, Cholesterol, which in turn is synthesized from acetyl-CoA (Section 21.16). The chemical structures of the major sex steroid hormones are shown in Fig. 25-25.

Androgens stimulate growth and maturation, maintain the function of the Reproductive System, and promote The Development of male secondary sex characteristics; estrogens regulate The activity of the FEMALE REPRODUCTIVE SYSTEM. At the same time, both androgens and estrogens exert significant and diverse effects on most non-reproductive Tissues throughout the body. For example, androgens stimulate Skeletal Muscle growth. Androgens and some of their derivatives are also known as anabolic steroids. They are used by many weightlifters, football players, and wrestlers to increase muscle mass and strength. However, in most sports, The Use of anabolic agents provides no significant advantage. It is also known that some female athletes have used anabolic steroids—apparently with success—though it must be noted that these hormones cause adverse masculinizing side effects.

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Fig. 25-25. The three major sex hormones. A. Testosterone is the primary androgen (male sex hormone). B. β-Estradiol is the primary estrogen (female sex hormone), formed from testosterone. C. Progesterone is the hormone of the corpus luteum. In the female body, it serves as a precursor for both testosterone and β-estradiol.

A third sex hormone, progesterone (Fig. 25-25), serves as a precursor in The Biosynthesis of adrenocortical steroids and sex hormones. One of its additional Functions is to stimulate ovum implantation.