There were letrozole-induced PCOS characterized by irregular estrus cyclicity, elevated (p<0.05-0.01) glycaemia, ovarian weight, triglycerides, total cholesterol, LDL cholesterol, VLDL cholesterol, malondialdehyde, luteinizing hormone (LH), and testosterone concentrations, but there were low (p<0.05-0.001) HDL cholesterol, estradiol, progesterone, catalase, peroxidase, and superoxide dismutase levels, compared with control. The gene discussed is CAT; the disease is polycystic ovary syndrome.