Estrogen Types and Their Connection to Breast Cancer

How Changing Levels of Estrogen Can Affect Your Health

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Estrogen is a group of hormones that are responsible a woman's development and ability to have children. Estrogen also helps regulate your menstrual cycle, protects bones from thinning and keeps cholesterol levels low to protect your heart. While estrogen is a normal and necessary hormone, estrogen can sometimes help turn normal breast tissue into cancers. Estrogen is made in three ways: within your body, in nature and in a synthetic form used in medications.

Three Kinds of Estrogen in the Female Body


  • Estrone: Estrone is made in the ovaries before menopause and after that by the adrenal glands. Postmenopausal estrone is stored in body fat and muscle cells. Women who have more body fat will still experience hot flashes during menopause, even though their body is storing more estrone than slimmer women. Estrone production goes down during pregnancy, which reduces your lifetime exposure to estrogen.
  • Estradiol: Like estrone, estradiol is made in the ovaries and less is created during pregnancy.
  • Estriol: Estriol is made by the placenta during pregnancy. This kind of estrogen is produced in the greatest quantities, more than estrone or estradiol, during pregnancy. Estriol production is an indicator of the health of your baby

During Menopause

As you approach menopause, your ovaries will shrink and production of estrogen and progesterone will fluctuate during that process.

It is the lower levels of these hormones that cause hot flashes, irregular periods, night sweats, mood swings and other symptoms. Doctors may treat these symptoms with hormone replacement therapy (HRT) for a short period of time, but prolonged use has been associated with increased risk of breast cancer.

Cancer Risk

Estradiol increases your risk of developing breast cancer in postmenopausal women. While doctors do not use blood estrogen levels to discover your risk of breast cancer, it's important to recognize the role of these hormones in causing cancer. To maintain healthy estrogen levels, doctors recommend that you take some steps to minimize your risk of developing breast cancer:

  • Maintain a healthy weight
  • Limit your alcohol intake
  • Exercise regularly
  • Avoid post-menopausal hormone therapy if your doctor thinks you're at risk


Fuhrman BJ, Schairer C, Gail MH, et al. "Estrogen metabolism and risk of breast cancer in postmenopausal women". National Cancer Institute. 2012, 326-339. 

Three kinds of estrogen are made outside of your body -- in plants, in our environment, and created synthetically in the lab.

Phytoestrogens - from plants and botanicals that have an estrogen-like effect on your body. Some plants that contain phytoestrogens are soy beans, red clover, beans, cereal brans and flaxseeds. The effects of these plant estrogens are quite a bit weaker than estrogen produced by your ovaries.

In alternative medicine, products that contain phytoestrogens may be used to treat menopausal symptoms. Not all of those herbal treatments are safe in regards to breast cancer.

Xenoestrogens – from chemicals present in our environment, many of which are petrochemicals. Xenoestrogens are much more potent than the estrogen your body makes, and too much exposure to them can result in problems with development, reproduction, and may cause cancer. We use products that contain xenoestrogens daily: plastics, electronics, medicines, foods, soaps and pesticides. Our environment (water, air, soil and plants) is being polluted by xenoestrogens from manufacturing runoff and the disposal of products containing xenoestrogens.

Synthetic Estrogens – made by pharmaceutical companies and included in prescription drugs. This kind of estrogen, like the xenoestrogens, is more powerful than natural estrogens. Before 2002, HRT was prescribed for a variety of reasons including treatment of menopause symptoms, and to help prevent heart disease, bone thinning, and certain cancers.

The Women's Health Initiative Study, published in 2002, revealed that HRT actually increased the risk of breast cancer and provided limited or no benefit for heart disease or stroke. It is interesting that when large numbers of women stopped using HRT, the rates of new cases of breast cancer began to decline.

Estrogen Types - Female Hormones - Estrone, Estradiol, Estriol

National Center for Complementary and Alternative Medicene. Do CAM Therapies Help Menopausal Symptoms? Last Updated: Nov. 2005.

Northwestern Health Sciences University. Stay Healthy Basics. Different Types of Estrogen and Their Functions. Last Updated: 2007.

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