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Gonadotrophin-releasing hormone (GnRH) antagonists (receptor blockers) are a class of drugs that antagonize the gonadotropin-releasing hormone receptor (GnRHR) and thus the action of GnRH. Some are similar in structure to natural GnRH (a hormone made by neurons in the hypothalamus) but that have an antagonistic effect. These GnRH antagonists are peptide molecules that are made up multiple, often synthetically produced amino acids. Others are small-molecule, non-peptide compounds. GnRH antagonists compete with natural GnRH for binding to GnRH receptors, thus decreasing or blocking GnRH action in the body. ==Mode of action== GnRH antagonists competitively and reversibly bind to GnRH receptors in the pituitary gland, blocking the release of luteinising hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary.〔Broqua P, Riviere PJ, Conn PM, et al (April 2002). Pharmacological profile of a new, potent, and long-acting gonadotropin-releasing hormone antagonist: degarelix. J. Pharmacol. Exp. Ther. 301: 95-102.〕〔Engel JB, Schally AV (February 2007). Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone. Nat. Clin. Pract. Endocrinol. Metab.: 3: 157-167.〕 In men, the reduction in LH subsequently leads to rapid suppression of testosterone release from the testes; in women it leads to suppression of estrogen release from the ovaries. Unlike the GnRH agonists, which cause an initial stimulation of the hypothalamic-pituitary-gonadal axis (HPGA), leading to a surge in testosterone or estrogen levels, GnRH antagonists have an immediate onset of action, rapidly reducing sex hormone levels without an initial surge.〔Van Poppel H, Nilsson S (June 2008). Testosterone surge: rationale for gonadotropin-releasing hormone blockers? Urology 71: 1001-1006.〕〔Gustofson RL, Segars JH, Larsen FW (November 2006). Ganirelix acetate causes a rapid reduction in estradiol levels without adversely affecting oocyte maturation in women pretreated with leuprolide acetate who are at risk of ovarian hyperstimulation syndrome. Hum. Reprod. 21: 2830-2837.〕 Currently approved GnRH antagonists include the following: * Cetrorelix * Ganirelix * Abarelix * Degarelix Elagolix, a non-peptide, orally-active GnRH antagonist that is still in development, is currently in phase III clinical trials. Other non-peptide, orally-active GnRH antagonists that are also in development include relugolix (TAK-385), KLH-2109, and ASP-1707. 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-releasing hormone antagonist」の詳細全文を読む スポンサード リンク
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