GNRH1 and endometriosis: GnRH agonists bind to receptors in the pituitary gland, thereby downregulating the pituitary–ovarian axis and causing hypoestrogenism [22], with the subsequent induction of amenorrhea and progressive endometrial atrophy thought to inactivate pelvic lesions and relieve endometriosis-associated pain [7,8,10,22,83].