Estrogens are natural hormones. They 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.
Blood estrogen levels and breast cancer risk in postmenopausal women
Studies have shown that postmenopausal women who have high levels of the estrogen estradiol in their blood have an increased risk of breast cancer . A pooled analysis that combined data from nine studies found the risk of breast cancer was twice as high among women with higher levels of estradiol compared to women with lower levels .
At this time, blood estrogen levels are not used by health care providers to assess breast cancer risk. However, certain factors can be used to estimate your exposure to estrogen. For example, because estrogen is produced in fat tissue, your body weight indirectly suggests how much estrogen you are exposed to (in general, higher weight means more estrogen exposure). In postmenopausal women, body weight is also linked to breast cancer risk (learn more).
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 two largest studies to date, findings were mixed [92-93]. One study found blood estrogens in premenopausal women increased breast cancer risk and the other study found no impact on risk.
Studies in premenopausal women are challenging because estrogen levels vary over the menstrual cycle. For example, in the early phase (follicular) of the menstrual cycle, estrogen levels are much lower than in the late phase (luteal).
Factors that affect blood estrogen levels
Your blood estrogen level is affected by many factors, some of which are within your control. All women can lower their estrogen levels by [46,94]:
All of these steps may help lower the risk of breast cancer as well as other chronic diseases.