Estrogen Does Not Cause Breast Cancer in MHT

Modern MHT employs estrogens, largely in a transdermal manner and natural progesterone. There are two forms of "progestogens" : synthetic "progestins" and natural "progesterone".  A "progestogen" is a class of chemical compounds that acts on the progesterone receptor in a similar manner to progesterone.

Synthetic Progestogens (Progestins) are man-made compounds designed to mimic the effects of progesterone. Synthetic progestins are used in various forms of contraception (like birth control pills) and in the past - in hormone replacement therapy (HRT) or MHT. While they are effective in mimicking many of progesterone’s effects, they are not identical to natural progesterone in structure, and their effects can vary.

The discovery of progesterone as a hormone and its role in human biology came from various scientific advances: 

1900s - Discovery and Isolation: In 1929, American scientists Willard Myron Allen and George W. Corner were the first to isolate and identify progesterone in the corpus luteum of the female body.

1940s - Synthetic Progesterone Development: By the 1940s, synthetic versions of progesterone were being developed for use in medicine. These early synthetic progestins were created as oral contraceptives and hormone replacement therapy, though they differed in structure and function from natural progesterone.

Bioidentical Hormones - 1980s and Beyond: The term "natural progesterone" often refers to bioidentical progesterone, which is synthesized from plant sources (such as wild yam or soy) but is chemically identical to the progesterone produced by the human body. This became more widely known and popular in hormone replacement therapy (HRT) by the 1980s and 1990s, particularly as a more natural alternative to synthetic progestins.

The development of natural, bioidentical progesterone derived from plant sources allowed for more natural hormone therapies that were closer in molecular structure to what the body naturally produces. Prometrium, a bioidentical form of progesterone, was developed in France by the pharmaceutical company Besins Healthcare. It is a micronized progesterone, which means the progesterone particles are made smaller to improve absorption when taken orally. Prometrium became widely available in the 1990s as a part of hormone replacement therapy (HRT) and is commonly used to treat conditions like progesterone deficiency, menopausal symptoms, and as part of fertility treatments. Besins Healthcare, a global company specializing in reproductive health, was responsible for its development and continues to manufacture it for use in several countries worldwide. Prometrium (micronized progesterone) was approved by the U.S. Food and Drug Administration (FDA) in 1998. Prometrium provides bioidentical progesterone, which helps protect the uterine lining (endometrium) from the risks associated with unopposed estrogen therapy, such as endometrial hyperplasia. As opposed to synthetic progestins, which are linked to increased risks of breast cancer in MHT, natural progesterone is not. 

Breast Cancer Fears: A primary hindrance to MHT that are still present.  

  • Lack of knowledge of benefits and risks of MHT is the primary hindrance to MHT for women.

  • This lack of knowledge leads to women being either not offered or declining MHT.

  • A large fear of breast cancer caused by MHT remains.

  • Despite an abundance of knowledge and safety data, women and health care professionals remain unnecessarily fearful of MHT.

Estrogen in MHT does not cause breast cancer.

  • Multiple studies have shown that menopausal hormone support with estrogen alone does not increase breast cancer risk.

  • This is safe for women who do not have a uterus.

  • For women with a uterus, a progestogen is needed to protect from estrogen induction of uterine cancer.

Estrogen + Synthetic Progestins in outdated regimens - which we rarely use today in MHT - does increase risk of breast cancer.

  • The use of synthetic progestins in MHT regimens are associated with a 1.26 fold elevated risk to develop breast cancer as demonstrated in the WHI Study. Multiple other studies have shown that synthetic progestins are associated with an elevated risk of developing breast cancer of a similar magnitude. Although these studies provide useful information, our modern preparations do not use synthetic progestins.

Estrogen + natural progesterone in modern MHT does not increase breast cancer risk.

  • Natural progesterone is believed to have a more favorable safety profile and has not been associated with the same elevated breast cancer risk as synthetic progestins, and many studies have shown no increased risk of breast cancer with estrogen + natural progesterone.

Estrogen + natural progesterone in MHT does not cause breast cancer.

  • Natural oral progesterone, employed in modern HT, was first developed in France and has been used there since 1980.

  • In contrast, many other European countries and the United States employed synthetic progestins in their HT regimens and studies.

  • Natural micronized progesterone is a progesterone which is identical to the progesterone made by the ovary and is synthesized from yams. It is micronized for oral absorption and was FDA approved in 1998, and marketed under the trade name Prometrium (TM).

Estrogen + natural progesterone in MHT does not cause breast cancer.

  • Data from the large E3N study conducted in France and published in 2008, demonstrated that HRT regimens employing natural progesterone are safer for breast cancer risks when compared to those employing synthetic progestins. The E3N study was a prospective cohort study of French female teachers and found that women who used HRT regimens employing natural progesterone had no elevated risk of breast cancer, as opposed to women who used regimens with synthetic progestins.

Estrogen + natural progesterone in MHT does not cause breast cancer.

  • This is very important information and IS applicable to modern HT.

  • These favorable findings were also confirmed in additional French studies: No increased risk was apparent among EP therapy users treated with natural micronized progesterone.

  • More recent data supports that estrogen + natural progesterone is safe for the breast, and does not increase the risk of breast cancer for at least up to five years of use.

Conclusions

  • Employ menopausal hormone support in an educated manner with support of facts not with fear of myths.