The Marion Gluck Clinic

Effects of estradiol with micronized progesterone or medroxyprogesterone acetate on risk markers for breast cancer in postmenopausal monkeys.

This study compared the effects of oral estradiol (E2) with either medroxyprogesterone acetate (MPA) and micronised progesterone on risk biomarkers for breast cancer in a post-menopausal primate model. 26 ovariectomised adult female cynomolgus macaques were divided into groups and rotated randomly through treatments of placebo, estradiol (1mg/day), estradiol + progesterone (200mg/day), and estradiol + medroxyprogesterone acetate (2.5mg/day). All treatments were administered orally for a period of two months and separated with a wash-out period of one month. Breast epithelial proliferation was measured by Ki67 expression. Compared to the placebo, estradiol + MPA administration resulted in significantly greater breast proliferations, whereas estradiol + progesterone did not. Overall this suggests that oral micronised progesterone has a more favourable effect on risk biomarkers for menopausal breast cancer than MPA.

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