PTGS2 and endometriosis: Initial studies and CTs had described the AIs as promising therapeutic agents for treatment of endometriosis [2, 4] since they could suppress the local estrogen produced by aromatase-positive implants and subsequent proliferative effect, as well as blocking the action on Cyclooxygenase-2 (COX-2) and prostaglandin E2, the later being responsible for inflammation [7, 18].