Progesterone News
Progesterone Vs. Progestins in Monkeys
Wood CE, Register TC, “Effects of estradiol with micronized progesterone or medroxyprogesterone acetate on risk markers for breast cancer in postmenopausal monkeys,” Breast Cancer Res Treat (2007) 101:125–134
This is an important, even landmark study, not in the sense of bringing us new information, but in confirming what’s already known but not substantially proven in published research to the satisfaction of those who don’t quite grasp yet how safe and effective progesterone is in hormone replacement therapy.
Macaque monkeys are about as close as it can get to reproducing in animal research what will happen in humans. The goal of this study was to compare the effects of different types of HRT. Twenty-six macaque monkeys without ovaries were divided into groups and rotated through four HRT regimens lasting two months each, with a one-month washout period in-between. The four groups received either: 1) placebo, 2) estradiol, 3) estradiol and oral micronized progesterone (natural progesterone in a pill, 200 mg daily) or 4) estradiol and medroxyprogesterone acetate (MPA also known as Provera).
Breast epithelial proliferation, a type of cell growth that’s a marker for breast cancer risk, was measured in each group after each type of treatment. Compared to placebo, treatment with estradiol and MPA resulted in significantly greater breast proliferation; treatment with estradiol and progesterone did not.
The conclusion of the authors: “These findings suggest that oral micronized progesterone has a more favorable effect on risk biomarkers for postmenopausal breast cancer than medroxyprogesterone acetate.”
Progesterone vs. Progestins in Humans
Fournier A, Berrino F et al, “Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study,” Breast Cancer Res Treat 2007 Feb 27; [Epub ahead of print]
This is a continuation of the large, ongoing French study of HRT known as the E3N Cohort Study, which has already published results twice, each time more clearly and definitively confirming that progestins increase breast cancer risk significantly, while progesterone does not.
This data involves 80,377 postmenopausal women, 2,354 of whom got invasive breast cancer during the average eight years of followup. Compared with women who had never used HRT of any kind, those who used estrogen alone (presumably women who had a hysterectomy) had a significant 1.29-fold higher increased risk of breast cancer. Women using estrogen-dydrogesterone (a progestin), had a 1.16-fold increased risk; women using estrogen and other progestins had a 1.69-fold increase; and women using an estrogen-progesterone (pill) combination had a risk of 1.00.
The authors conclude that, “These findings suggest that the choice of the progestagen component in combined HRT is of importance regarding breast cancer risk; it could be preferable to use progesterone or dydrogesterone.”
This information comes from a pre-publication online abstract, so it will be interesting to find out the details of the data when the research is published in its entirety.
From NPAN template | Jul 17, 2007