Structures, Functions and Expressions of GnRH and GnRH Receptor in Peripheral Reproductive Organs and Their Regulation by Estradiol17β

Studies have shown that estradiol17β (E2) regulates gonadotropi-nreleasing hormone (GnRH) and GnRH receptor expression in hypothalamus and pituitary. Several studies have shown that GnRH and its receptor are also expressed in peripheral reproductive organs and little is known about their regulations. In this study, GnRH and GnRH receptor structures, functions, their peripheral expressions and regulations by E2 were reviewed. Several in vivo and in vitro conducted studies indicate that E2 decreases the expression of GnRH mRNA and regulates GnRH receptor expression in a time dependent manner. Nevertheless, the exact mechanism has not been clearly explained yet.