The nonsignificant decrease (P < 0.0001) in GPx1 relative gene expression was observed in the patients with endometriosis compared with the control group (0.351 ± 0.032) and significant increase in GPx1 relative gene levels (0.215 ± 0.043) in the patients with endometrial cancer (0.822 ± 0.111). The gene discussed is GPX1; the disease is endometrial cancer.