Breast Cancer

A large team of scientists have determined that natural progesterone has the potential to slow the growth of many breast cancer tumors or even shrink them, unlike synthetic progestins which increase breast cancer risks, .

It has long been known that tumors with estrogen receptors (ER) and progesterone receptors (PR) – termed ER/PR double positive – have the best clinical outcome. A study conducted by researchers from prestigious institutions including the Cancer Research UK Cambridge Institute; University of Adelaide, Australia; University of Texas, Southwestern Medical Center at Dallas; and University of North Carolina at Chapel Hill explain why double positive breast cancer patients have the best chance of survival. The finding could benefit up to half of all breast cancer patients.

Scientists know that when activated by most forms of estrogen – especially estradiol and its metabolites – estrogen receptors turn on genes within cancerous cells that program those cells to multiply rapidly and stay alive rather than die off as normal, healthy cells do. When activated by progesterone, progesterone receptors attach themselves to estrogen receptors. Once this happens, estrogen receptors stop turning on genes that promote the growth of the cancer cells. Instead, they turn on genes that promote the death of cancer cells (apoptosis) and stimulate the growth of healthy, normal cells.

The researchers pointed out that only natural, bio-identical progesterone slows the growth of breast cancer. Conversely, synthetic progestins (molecularly altered forms of progesterone including medroxyprogesterone acetate and other progesterone derivatives found in birth control pills) have been shown to increase rather than decrease breast cancer risks.

This is exciting news for women who are diagnosed with ER/PR positive breast cancers. If such women have healthy progesterone levels, or when progesterone levels are increased through natural progesterone supplementation, treatment outcomes may improve significantly.

Hormonal imbalances have reached epidemic proportions in most developed countries over the last several decades. Due to poor diets, lack of exercise, a rise in obesity levels, the widespread use of hormone-altering chemicals, and other factors, many women suffer from chronically higher than normal estrogen levels and much lower than normal progesterone levels.

In their book What Your Doctor May Not Tell You About Breast Cancer, John R. Lee, M.D. and David Zava, Ph.D. noted that women with progesterone levels that are low relative to estrogen levels are more likely to get breast cancer and have poorer treatment outcomes. They concluded that estrogen dominance causes estrogen receptors to activate genes such as BCL-2 that are known to promote the rapid growth of cancer cells. They theorized that chronic states of estrogen dominance contribute to high rates of breast cancer, and their theory has been validated with this latest research.

ReferencesNature 2015; 523; 313-317.
Pharmaceutical Journal, 17 Jul 2015.

John R. Lee, M.D.; David Zava, Ph.D.; and Virginia Hopkins. “What Your Doctor May Not Tell You About Breast Cancer.” 2002
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