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Gonadotropins are glycoprotein polypeptide hormones secreted by gonadotrope cells of the anterior pituitary of vertebrates. This family includes the mammalian hormones follicle-stimulating hormone (FSH), luteinizing hormone (LH), and placental/chorionic gonadotropins human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG), as well as at least two forms of fish gonadotropins. These hormones are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function. LH and FSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta in pregnant humans and mares, respectively. The gonadotropins act on the gonads, controlling gamete and sex hormone production. Gonadotropin is sometimes abbreviated ''Gn''. The alternative spelling ''gonadotrophin'' which inaccurately implies a nourishing mechanism is still sporadically used. ==Natural types and subunit structure== The two principal gonadotropins in vertebrates are luteinizing hormone (LH) and follicle-stimulating hormone (FSH), although primates produce a third gonadotropin called chorionic gonadotropin (CG). LH and FSH are heterodimers consisting of two peptide chains, an alpha chain and a beta chain. LH and FSH share nearly identical alpha chains (about 100 amino acids long), whereas the beta chain provides specificity for receptor interactions. These subunits are heavily modified by glycosylation. The alpha subunit is common to each protein dimer (well conserved within species, but differing between them〔), and a unique beta subunit, which confers biological specificity.〔 The alpha chains are highly conserved proteins of about 100 amino acid residues which contain ten conserved cysteines all involved in disulfide bonds, as shown in the following schematic representation. +---------------------------+ +----------+| +-------------|--+ | || | | | | | | | +------|-----------------+ | | | +----------------------------+ 'C': conserved cysteine involved in a disulphide bond. Intracellular levels of free alpha subunits are greater than those of the mature glycoprotein, implying that hormone assembly is limited by the appearance of the specific beta subunits, and hence that synthesis of alpha and beta is independently regulated.〔 Another human gonadotropin is human chorionic gonadotropin (hCG), produced by the placenta during pregnancy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「gonadotropin」の詳細全文を読む スポンサード リンク
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