Based on results from RCTs in women with endometriosis, the progestin norethindrone acetate (NETA), known as norethisterone acetate in Europe, was approved by the Food and Drug Administration at a daily dose of 5 mg, combined with synthetic GnRH agonist (leuprolide acetate), as add-back therapy in women with endometriosis [41]. This evidence concerns the gene GNRH1 and endometriosis.