Estrogens are natural hormones. They are important in sexual development and other body functions. Before menopause, estrogens are produced mainly in the ovaries in women. After menopause, they are produced mainly in fat tissue.
Higher amounts of estrogen in the blood are linked to an increased risk of breast cancer in women after menopause . Researchers are studying a possible link to breast cancer before menopause.
For a summary of research studies on estrogen levels and the risk of breast cancer, visit the Breast Cancer Research Studies section.
Studies have shown that postmenopausal women who have high blood levels of the estrogen estradiol have an increased risk of breast cancer [17,48-50]. 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, higher body weight is also linked to increased breast cancer risk (learn more).
A pooled analysis of data from seven studies found that higher blood estrogen levels may modestly increase breast cancer risk in premenopausal women .
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).
Blood estrogen levels are affected by many factors. Some of these are under your control. All women can lower their estrogen levels by :
All of these steps may help lower the risk of breast cancer and other chronic diseases.