The Balance of Estrogen and Progesterone and Their Impact on Breast Cancer

Breast cancer seems to be out-of-control in terms of prevalence these days. Second only to skin cancer in prevalence, approximately one in eight women will develop invasive breast cancer during their lifetime (statistics from the American Cancer Society). It’s so important to understand the balance of estrogen and progesterone and their impact on breast cancer.

Estrogen and progesterone are two reproductive hormones that are produced in both men and women, but in larger amounts in women. One of the factors influencing breast cancer susceptibility and outcomes in women are estrogen receptors. Estrogen receptors are molecules within cells (including tumor cells); the presence of estrogen can trigger these receptors, allowing them to switch genes on and off. Estrogen binding to the estrogen receptor can switch on a panel of genes that tell the cells to keep dividing, thus fuelling tumor growth. This is why certain treatment protocols for breast cancer involve blocking estrogen receptors, and reducing estrogen levels in the body.

Approximately 7 out of 10 women with breast cancer have estrogen-dependent breast cancer.

Lesser understood, but equally important, is newer research on the progesterone receptor. Women with high levels of both estrogen and progesterone receptors fare better and have better outcomes than women with only estrogen-receptor positive cancer. Why is this?

A research study demonstrated that when a cell was exposed to estrogen and progesterone, and both receptors were activated, the progesterone receptor actually stuck to the estrogen receptor. This then affected how the receptor attached to the DNA, which influenced the gene switches that regulate the growth of cancer cells. This study was published in Nature.

What this means is that scientists are getting a better understanding of how different hormones influence breast cancer. This could have a huge impact on the development of treatments for breast cancer, and our understanding of ways to prevent it.

Putting that in every day terms for those of us trying to prevent health issues such as cancer, one thing stands out to me here. It is important to make sure our bodies do not get in a state of chronic estrogen dominance. Synthetic estrogens such as from plastics, or from meats that have been given hormones, can bind to estrogen receptors; if we have too much estrogen, without sufficient progesterone, we may be at a higher risk of breast cancer. This certainly seemed to be evident from the Women’s Health Initiative back in 2002 that found that hormone therapy (much of which was based on synthetic estrogens) actually increased rates of breast cancer, to the point of cancelling the study for ethical reasons.

It also means that women in their 30’s and 40’s should be keeping a close eye on their estrogen and progesterone levels, since it is so common for progesterone levels to fall in those decades and turn into a state of estrogen dominance. Herbs such as Chaste Tree (Vitex) or bio-identical progesterone may help to balance and protect against excess estrogen. Women who are using estrogen therapy to help curb symptoms of menopause are best using progesterone in tandem with it, so as to not create a scenario of excess estrogen in the absence of the protective effect of progesterone.

Breast cancer rates are on the rise. Studies such as this one go a long way to help scientists and doctors prevent and treat it successfully, so let’s hope that fewer women are negatively impacted by breast cancer in years to come. While there are definitely genetic predispositions, we also need to cognizant of our nutrition and external sources of toxicity to try and mitigate our risk factors as much as possible.