Subscribe to the articles on this site »

Hormones and Breast Cancer: The Latest Findings from WHI

by Dr David Zava on 30/10/10 at 4:06 pm

Hormones and Breast Cancer: The Latest Findings from WHI

I was sent a link to the Today Show, broadcast on October 20th which featured an interview with Dr. Nancy Snyderman, discussing further findings from the Women’s Health Initiative Study (WHI), published in the Journal of the American Medical Association (JAMA) this week. This news may confuse your patients and I wanted to take this opportunity to explain the study and assure you this study does not include natural hormones, but refers to the combination of Premarin and Provera.

The experts stated that there is an increase in risk of death from breast cancer when you are taking the combination of estrogen and progestin. In this case, the drugs that were used were Premarin and Provera. Premarin is known as conjugated equine estrogens and is horse estrogen which has some similarities to human estrogen but is not the same. Provera is a progestin known as medroxyprogesterone acetate and is very different in function from natural progesterone.

“Experts” who are saying that synthetic progestins increase breast cancer risk are right, but, we’ve known that since 2002. Unfortunately, these same “experts” are now claiming an association of natural progesterone with breast cancer by default. They espouse that there is no clinical evidence to show natural progesterone is any safer than synthetic progestins. Unfortunately, this is an incorrect assumption and they have not done their homework. Natural progesterone has a much safer profile than all forms of synthetic progestins, not only for the breasts, but for nearly all tissues of the body, including the reproductive tissues, the cardiovascular systems, and the brain. There is a plethora of published literature on this subject.

For those who are unsure about the striking differences in safety profiles of synthetic progestins versus natural progesterone as regards breast cancer risk, several clinical trials have clearly shown the superiority of natural progesterone.

In a 2005 review of clinical studies comparing synthetic progestins to natural progesterone, Campagnoli and coauthors (J Steriod Biochem Mol Biol 96, 95-108) concluded that: “The balance of the in vivo evidence is that progesterone does not have a cancer-promoting effect on breast tissue. …..We therefore suggest that when HRT is indicated, preparations containing progesterone and not a synthetic progestin should be used, according to a sequential or cyclic-combined regimen. In this way the risk of endometrial cancer is minimized without increasing the risk of BC.”

In another 2005 clinical trial comparing synthetic progestins to the natural progesterone, Fournier and coworkers (Int J Cancer 114, 448-454) found that: “The risk was significantly greater than p0.001 with HRT containing synthetic progestins than with HRT containing micronized progesterone, the relative risk being 1.4 and 0.9, respectively.” Yes, that’s right; progesterone users had a lower risk.

So why are the news media confusing synthetic progestins with natural progesterone? Too often information such as this is streamlined in mainstream media by those who have power, money and the ability to shout through the megaphone the loudest. We know all too often that large pharmaceutical companies have a strangle hold on funding for universities, who gets grants, what gets published, whose opinions get press, the success of women’s health organizations and journals they represent. Unfortunately, because of this ability to present one-sided research in such a commanding way, it is not unusual that the news media doesn’t spend much time researching the science and the evidence based data and studies that are available; and in this case, available about the difference between progestins and natural progesterone as well as the benefits of natural progesterone.

The decision on natural hormone therapy is one between a patient and physician; you cannot extrapolate what happens in the body using Premarin and Provera to discuss what happens in the body with its own natural hormones. Natural hormones, when properly balanced, allow the body to function at its optimal level.

Thank goodness for women’s intuition that senses right from wrong.

Post to Twitter

14 Responses to “Hormones and Breast Cancer: The Latest Findings from WHI”

  1. avatar


    Jan 18th, 2012

    Dr. Zava,

    Can you say more about the pros and cons of natural progesterone used topically vs taken orally? We’ve always been told that topically is better.

  2. avatar


    Feb 24th, 2011

    I have been taking progesterone (topical progesterone and/or prometrium 100mg 2-3xday for 3 weeks out of the month) since I was 34 years old and I’m soon to be 51. I needed to take progesterone as a results of headache, mood fluctuations, etc..(I’m one of the 10% of women that sense any increase in estrogen)–diagnosed with PPDD & polycystic ovary disease (which makes a lot of sense why I was having early perimenopausal symptoms. I have had no evidence of any breast CA and actually at one time I had increased breast cyst (very painful during a mammography and was called back for an ultrasound–which was negative). I new that it was because I was npt taking enough progesterone during that particular stressful month. I had signs of osteopenia at age 34 and I do believe it is the progesterone that has helped rebuild as well as maintain my bones to a healthy density! One year I even stopped taking my calcium regularly to see if my bone density would be affected; to my relief my bone density increased (I do also exercise at least 3 x a week). I could not live without natural progesterone and maintain such a healthy lifestyle, both mentally and physically! I have counseled many women to use it (as they trust there nurse friend). I have have witnessed two women friends state that not only had their sleep & anxiety levels improved–both saw there rosecea disappear! I currently have a 60yr. old friend with osteoporosis and has not had no improvement in her bone density with conventional tx and is now applying progesterone 3 week out of the month per my suggestion (I did have her consult her MD). We are both looking forward to her next yearly bone scan! Any women concerned with her bone density, perimenopausal symptom, hx or no hx of breast CA should consider looking into the benefits of natural progesterone! Sincerely–Eva Dines
    Sincerely–Eva Dines

  3. avatar

    Sharryn Mahorney

    Nov 3rd, 2010

    In 1998 I was diagnosed with infiltrating duct cell carcinoma after having taken Provera for 6 years. What’s the deal?!? I refused chemo, radiation and tamoxifen. But began over-the-counter progesterone cream. Six years later I again had the very same small tumor in the very same location and this time took the multiple radiation treatments but still refused the chemo and tamoxifen. It has now been almost 7 years since the second occurrence and continue to take progesterone as a prescription. I look forward to many more healthy years with the help of the natural progesterone.

  4. avatar

    Carol LaMar

    Nov 1st, 2010

    In 2008 I had a lumpectomy for infiltrating ductal carcinoma. 33 radiation treatments, now taking Armidex . I really don’t know who to trust. I feel like stopping the Arimidex, which is supposed to rid my body of Estrogen. The Premarin was supposed to be a wonderful miracle for me!! No history of BC in my family! It’s all about making the Drug Companies RICH.