BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 15. INTEGRATION OF METABOLIC PATHWAYS. HORMONES

15.10. Sex Hormones

Sex Hormones are synthesized primarily in the Gonads of females (Ovaries) (Fig. 15.14) and males (Testes) (Fig. 15.15). There are two groups of Female Sex Hormones: estrogens (the principal representative is estradiol) and progestins (the principal representative is progesterone). Estradiol is synthesized predominantly in the follicles. Cholesterol also serves as a precursor for these hormones.

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Fig. 15.14. Structure of female sex hormones

The Synthesis and Secretion of sex hormones are regulated by the pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which, in turn, are regulated by hypothalamic gonadotropin-releasing hormone (GnRH). Gonadotropic hormones act via Membrane Receptors coupled with adenylate cyclase.

Fig. 15.15. Structure of Male Sex Hormones:

A - testosterone, B - dihydrotestosterone, C — androstenediol

In males, LH binds to Leydig Cell receptors to stimulate testosterone production, while FSH binds to Sertoli cell receptors in the testes to promote Spermatogenesis. Testosterone inhibits the synthesis and secretion of gonadotropin-releasing hormone and pituitary gonadotropins via a negative feedback mechanism. The inhibition of FSH secretion is mediated by the protein inhibin, which is produced by Sertoli Cells. FSH stimulates the synthesis of this protein, which in turn inhibits further FSH secretion through negative feedback.