Hormone And Gonadotropins

The gonadotropins are peptides that have a close functional relationship to estrogen, progesterone, and testosterone. They are called gonadotropins because of their actions on the gonads. As shown in Figures 25.9 to 25.11, they control ovulation, spermatogenesis, and development of sex organs, and they maintain pregnancy. An additional peptide, go-nadotropin-releasing hormone (GnRH), regulates release of the gonadotropins. Included in this group are the following:

• Luteinizing hormone (LH)

• Follicle-stimulating hormone (FSH)

• Chorionic gonadotropin (CG; hCG is human chorionic gonadotropin), a glycopeptide produced by the placenta; its pharmacological actions are essentially the same as those of LH

Gonadotropin-Releasing Hormone

The hypothalamus releases GnRH, a peptide that stimulates the anterior pituitary to secrete LH and FSH in males and females. This peptide controls and regulates both male and female reproduction (Figs. 25.9 and 25.10). GnRH is a modified decapeptide (10 amino acids): PyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2. The pyroglutamate at the N-terminus and the C-terminal amide distinguish this pep-

Hypothalamus GnRH

Anterior Lobe of Pituitary

Anterior Lobe of Pituitary

FSH LH

FSH LH

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