03/18/2010 05:12 am ET Updated Nov 17, 2011

Hormone Therapy: Synthetic Progestins Are Not The Same As Progesterone

It's 2002 all over again, and women are being warned against taking hormone replacement because of its link to breast cancer. Why is history repeating itself? Because we haven't learned an important lesson. Synthetic progestins are not the same as progesterone, and reporting on them as if they confer the same risks and benefits is absurd.

I'm talking about the study in the New England Journal of Medicine dated February 5, 2009, which concludes that hormone therapy doubles the risk of breast cancer. Specifically, women past menopause who take both estrogen and progestin (such as in the form of Prempro) for five years or more have twice the risk of developing breast cancer. When these same women stopped their combination hormone formula, the number of breast cancer incidents dropped by about 28 percent within the first year.

This study is a follow-up to the landmark Women's Health Initiative that studied more than 15,000 women between the ages of 50 and 79 who were taking HRT. In 2002, the study was stopped when researchers concluded that Prempro caused higher incidents of heart problems and breast cancer. Interestingly, the number of breast cancer cases dropped significantly since 2003.

Dr. Rowan Chlebowski, a medical oncologist at Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, wanted to know why. So he assembled a team of researchers to determine if it was due to women halting their HRT or to more vigilant mammography practices.

It's related to HRT use; getting regular mammograms didn't affect the numbers at all. But it's not related to all hormone therapy! The women who took only estrogen (usually in the form of Premarin) without the progestin were no more likely to develop breast cancer than women who took no hormones at all. (Progesterone lowers the risk of uterine cancer. Women without a uterus aren't typically given a progestin.) This means the synthetic progestin is the likely culprit.

Flashback to 2002. Women around the world stopped HRT cold turkey, causing many to feel unhealthy. Why? Because many healthcare providers and researchers didn't know or appreciate the difference between a synthetic progestin and progesterone, which is a bioidentical hormone.

Progesterone matches a woman's body exactly and has been shown to ease mood, sleep, and cycle-related issues. Progesterone supplementation has another unique advantage--it can be converted to other hormones, such as testosterone and DHEA, if needed.

Synthetic progestin is an altogether different substance known to actually exacerbate perimenopausal and post-menopausal symptoms--in addition to increasing your risk of breast cancer, heart disease, and stroke.

It's hard to believe that seven years have passed and yet the difference between synthetic progestins and progesterone is not widely understood. I've recommended progesterone instead of progestin for more than 20 years. It matches a woman's body better than a synthetic hormone ever could. And, as the study shows, doesn't increase the risk of breast cancer.

I encourage every woman to learn about the hormone therapy options available today. They are vast, and there are many excellent choices made from bioidentical hormones. I also encourage every woman to look with a critical eye when reading the news about HRT. It's likely that there will continue to be controversial and conflicting information.

For a primer on bioidentical hormones, read "The ABC's of HRT" in the Women's Wisdom Circle.

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Copyright Christiane Northrup, Inc. All rights reserved. Reproduction in whole or in part without permission is prohibited.

This information is not intended to treat, diagnose, cure, or prevent any disease.
All material in this article is provided for educational purposes only. Always seek the advice of your physician or other qualified health care provider with any questions you have regarding a medical condition, and before undertaking any diet, exercise, or other health program.


Chlebowski, Rowan T., 2009. Breast cancer after use of estrogen plus progestin in postmenopausal women, New England Journal of Medicine, February 5, Volume 360:573-587.