TRANSDERMAL ESTRADIOL AND MEDROXYPROGESTERONE ACETATE IN HORMONE REPLACEMENT THERAPY ARE BOTH ANTIOXIDANTS

We have evaluated the effects of the different components of hormone r eplacement therapy (HRT) on the production of free radicals in platele t membranes from menopausal women. The study included 12 women in meno pause for at least 6 months to a maximum of 4 years. First, the effect was determined of progestin only during the administration of 20 mg/d ay medroxyprogesterone acetate for 5 days. The peroxide production lev el was measured on day 0 and day 5. The second set of experiments was carried out in the first month of cyclic HRT with transdermal estradio l 50 mu g/day from day 1 to day 25 and medroxyprogesterone acetate fro m day 13 to day 25. In this experiment, the peroxide level was evaluat ed on days 0, 12 and 25. A significant reduction of peroxide level was observed after oval medroxyprogesterone acetate administration. Durin g HRT, we observed a similar reduction in lipid oxidation at the peak of the estrogen effect, and a further decrease with the administration of medroxyprogesterone acetate. It is concluded that reduction of lip id peroxidation during HRT is not only due to estrogens, but also depe nds upon the combined action of sex steroids. This observation justifi es not only the combined regimen (estrogens plus progestin) in HRT, bu t also the positive effects of progestins alone on patients who cannot use estrogens.