The control of reproduction includes a series of hormonal interactions between the central nervous system (hypothalamus and pituitary) and gonads. Gonadotropin-releasing hormone (GnRH) is a decapeptide produced by a few hundred hypothalamic neurons. These cells extend termini to the median eminence to secrete GnRH in a pulsatile fashion into the hypophyseal-portal venous system. GnRH is then carried to the anterior pituitary where the gonadotropes (which comprise 5–7% of the total cell population) respond to GnRH via high-affinity cell-surface GnRH receptors by effecting the synthesis and secretion of the gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). LH and FSH are dimeric peptides, comprised of a common α subunit and distinct β subunits, the latter conferring biological activity. Both LH and FSH are released in pulses into the systemic circulation, and act on the gonads in concert, with FSH predominantly regulating gamete development, but also being required to induce hormonal responses to LH. Thus, the combined actions of LH and FSH control both hormonogenesis (estradiol and progesterone from the ovary, testosterone from the testes, and inhibin, activin, and follistatin in both sexes) and gametogenesis. These steroid and peptide hormones have both local effects to promote gamete formation, and exert feedback regulation at the hypothalamus and pituitary.
KeywordsLuteinizing Hormone Granulosa Cell Serum Luteinizing Hormone Pregnant Mare Serum Gonadotropin Luteinizing Hormone Release
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