Estrogens are natural hormones that are important in sexual development and other body functions. Estrogens are produced mainly in the ovaries in premenopausal women, and mainly in fat tissue in postmenopausal women. Higher amounts of estrogen in the blood are linked to an increased risk of breast cancer in postmenopausal women. Researchers are studying a possible link to breast cancer among premenopausal women as well.
Blood estrogen levels and breast cancer risk in postmenopausal women
Studies have shown that breast cancer risk is increased among postmenopausal women who have high levels of the estrogen estradiol in their blood. In an analysis that combined data from nine studies, the risk of breast cancer was twice as high among women with higher levels of estradiol compared to women with lower levels [72].
At this time, blood estrogen levels are not used by health care providers to assess breast cancer risk. However, there are certain indirect markers that can be used to estimate how much estrogen you have been exposed to in your lifetime. For example, your age at your first period and your age at menopause indicate how many years you were exposed to the higher estrogen levels related to menstrual cycles.
Your blood estrogen level is affected by many factors, some of which are within your control. All women can lower their estrogen levels by maintaining a healthy weight, limiting alcohol intake and being physically active. Postmenopausal women can lower estrogen levels by avoiding postmenopausal hormones. All of these steps can help lower the risk of breast cancer as well as other chronic diseases.
Blood estrogen levels and breast cancer risk in premenopausal women
Few studies have looked at blood estrogen levels and breast cancer risk in premenopausal women. In the only two large studies to date, findings were mixed [73,74]. One study found that blood estrogens in premenopausal women increased breast cancer risk and the other study found no impact on risk. Studies in premenopausal women are more difficult to do because estrogen levels vary so much over the menstrual cycle. For example, estrogen levels are much lower in the early phase (follicular) than the late phase (luteal) of the menstrual cycle.
Updated 11/09/09
