CAT and endometriosis: The catalase (CAT) relative gene expression (Fig. 5) showed a tendency of substantial and significant decrease (P = 0.003) in the endometriosis group (0.033 ± 0.009) whereas only slightly decreased in the endometrial cancer samples (0.145 ± 0.021) compared with the healthy controls (0.225 ± 0.044).