Nafarelin is a gonadotropin-releasing hormone agonist (GnRH agonist) which acts as an analog of GnRH. Nafarelin increases the release of FSH and LH by the anterior pituitary, which in turn leads to an increase of estrogen/progesterone. When administered, Nafarelin has the purpose of causing increase estrogen that will negatively feed back upon hypothalamus to decrease GnRH ( negative feedback loop ) Through negative feedback, Nafarelin causes a decrease in pituitary secretion of gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH). Nafarelin may be used in the treatment of estrogen-dependent conditions (such as endometriosis or uterine fibroids), to treat central precocious puberty, and to control ovarian stimulation in IVF. It is normally delivered via a nasal spray. Nafarelin acetate is marketed by Searle (now part of Pfizer) under the brand name Synarel.