Effects of percutaneous estradiol–oral progesterone versus oral conjugated equine estrogens–medroxyprogesterone acetate on breast cell proliferation and bcl-2 protein in healthy women

In a prospective, randomized clinical study 77 women were assigned randomly to receive sequential hormone therapy with either conventional oral conjugated equine estrogens (0.625 mg) with the addition on 14 of the 28 days of oral medroxyprogesterone acetate (5 mg) or natural E2 gel (1.5 mg) with oral micronized P (200 mg) on 14 of the 28 days of each cycle. Because oral conjugated equine estrogens–medroxyprogesterone acetate induced a highly significant increase in breast cell proliferation in contrast to percutaneous E2–oral P with a difference between therapies approaching significance, the former therapy has a marked impact on the breast whereas natural percutaneous E2–oral micronized P has not.