Serum lipid peroxides and total antioxidant status in postmenopausal women on hormone replacement therapy.

Estradiol (E2) has antioxidant properties. The role of progestins in antioxidant defense is still unknown. We have evaluated the influence of E2 and E2 plus medroxyprogesterone acetate (MPA) on serum lipid peroxide (LPO) levels, a marker of free radical reactions, and serum total antioxidant status (TAS) in postmenopausal women. Subjects consisted of 26 women with surgical menopause, before and after 4 months of estrogen replacement therapy (ERT; E2), and 54 women with natural menopause on hormone replacement therapy (HRT; E2 plus MPA). Forty premenopausal women served as a control group. Serum E2 was estimated by radioimmunoassay, follicle-stimulating hormone by IRMA methods, LPO and TAS by colorimetric methods. Before therapy, LPO levels in the postmenopausal women were significantly higher (p < 0.001) than in the control group. After both ERT and HRT, LPO decreased significantly and did not differ between both groups and the control group. TAS was significantly lower in postmenopausal women (p < 0.001) than in the control group before therapy. After both ERT and HRT, TAS increased significantly and did not differ between both groups and the control group. We conclude that oxidative stress is increased after menopause. ERT and HRT inhibit the generation of free radicals and raise antioxidant potential to the levels found in premenopausal women. MPA did not influence the antioxidant action of E2.