The Role of Estrogen in Breast Cancer

Human Oestrogen Receptor
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Estrogen is a hormone that plays a vital role in women's health, including her breast and bone health. Let's learn about the role estrogen plays in women's health and how suppression of this hormone lowers the risk of breast cancer recurrence in certain women.

Estrogen is a hormone produced by a woman's ovaries until she reaches menopause. At menopause, defined as 12 months after a woman's last menstrual cycle, the ovaries stop making estrogen. This estrogen deficiency is what causes many symptoms of menopause, like hot flashes and vaginal dryness.

What Is Estrogen Therapy?

Some women take hormone therapy, usually prescribed during perimenopause or early menopause, to alleviate distressing menopausal symptoms, especially hot flashes. Hormone therapy can contain both estrogen and progesterone or just estrogen.

If a woman does not have a uterus—for instance, if she had a hysterectomy—than she may just take estrogen therapy (ET) alone. If a woman has a uterus, she needs to take progesterone in addition to estrogen. This is because estrogen therapy may lead to thickening of the lining of the uterus which could cause endometrial cancer. Adding progesterone counteracts these effect.

It's important to know that according to the U.S. Federal Drug Administration (FDA), hormone therapy is contraindicated in any woman with current breast cancer, a history of breast cancer, or suspected breast cancer.

How Estrogen Is Related to Breast Cancer

According to the American Cancer Society, approximately two out of three breast cancers are hormone receptor-positive. This means that the cancer cells have receptors for either or both the hormones—estrogen and progesterone.

Estrogen stimulates the growth of breast cancers that are estrogen receptor-positive. This is why menopausal hormone therapy is contraindicated in women with breast cancer or a history of breast cancer, so as to not increase a woman's risk of breast cancer recurrence.

Estrogen Suppression Therapy

Most types of hormone therapy for breast cancer, like selective estrogen-receptor modulators or aromatase inhibitors, either lower estrogen levels or stop estrogen from acting on breast cancer cells. This kind of treatment is helpful for hormone receptor-positive breast cancers, but it does not help patients whose tumors are hormone receptor negative (both ER- and PR-negative).

Estrogen Linked to Bone Health

A healthy level of estrogen in your body builds and maintains strong bones. However, if you've had chemotherapy or if you're taking estrogen suppression medication after treatment for breast cancer, your estrogen levels will be low. Guard your bone health by understanding how estrogen affects your bones.

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Article Sources

  • American Cancer Society. Breast Cancer: Hormone therapy for breast cancer. October 14th, 2015.
  • The North American Menopause Society. (2014). The Menopause Practice: A Clinician’s Guide, 5th ed. Mayfield Heights, OH: The North American Menopause Society.