GNRH1 and endometriosis: Additional treatment with a gonadotropin-releasing hormone (GnRH) agonist (GnRHa) before IVF-ET (ultralong GnRHa therapy) improved the outcome of IVF-ET in endometriosis patients, as shown by increased numbers of retrieved oocytes and transferred embryos, and higher implantation and pregnancy rates [23-25].