Nafarelin is a synthetic decapeptide agonist of the luteinizing hormone-releasing hormone (LHRH) which is approximately 200 times more potent than the natural peptide. Like LHRH nafarelin stimulates the release of the gonadotrophins luteinizing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary which in turn results in an initial increase of testosterone and estradiol synthesis. Continuous administration of LHRH or one of its analogs causes a sustained down-regulation of circulating LH and FSH levels leading to a suppression of testicular and ovarian steroidogenesis. Currently, nafarelin is indicated for the treatment of endometriosis and for the use in reproductive medicine. CAS Number (nafarelin acetate): 86220-42-0.