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 with higher blood levels of the estrogen estradiol have an increased risk of breast cancer [18,45-47].
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, health care providers do not use blood estrogen levels to assess breast cancer risk. However, this may be useful in the future .
Certain factors may increase breast cancer risk by affecting estrogen levels.
Body weight is one example. Estrogen is produced in fat tissue. In general, higher weight means more fat tissue and higher estrogen levels. This may explain the increased breast cancer risk in women who are heavy after menopause.
Learn more about body weight and breast cancer risk.
A pooled analysis of data from seven studies found that higher blood estrogen levels may modestly increase breast cancer risk before menopause .
Studies in premenopausal women are a challenge because estrogen levels vary over the menstrual cycle.
For example, in the early phase of the menstrual cycle (follicular), 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.