Disturbed balance between phase I and II metabolizing enzymes in ovarian endometriosis: A source of excessive hydroxy-estrogens and ROS?

► Expression of CYP1A1, CYP3A7, COMT and MB-COMT levels were higher in endometriosis. ► Expression of SULT1E1, SULT2B1, UGT2B7, NQO1, and GSTP1 was decreased. ► Three NQO1 isoforms were detected; NQO1c appears to be endometriosis-specific. ► This imbalance between phase I and II enzymes may lead to excessive ROS formation. ► Hydroxy-estrogens and ROS can promote proliferation of ovarian endometriotic cells.