Breast Cancer Risk Factors: Blood Estrogen Levels

Estrogens are natural hormones. They are important in sexual development and other body functions.

Before menopause, most estrogens in women are produced in the ovaries. After menopause, the ovaries no longer produce much estrogen, and estrogens mainly come from fat tissue.

After menopause, higher amounts of estrogen in the blood are linked to an increased risk of breast cancer in women [22].

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.

Learn about other factors linked to the risk of breast cancer.

Blood estrogen levels and breast cancer after menopause

Studies show postmenopausal women with higher blood levels of the estrogen estradiol have an increased risk of breast cancer [22,67-68].

A pooled analysis of data from 9 studies found the risk of breast cancer was twice as high among women with higher levels of estradiol compared to women with lower levels [22].

Today, health care providers don’t use blood estrogen levels to assess breast cancer risk. However, this measure may be useful in the future [71-73].

Certain factors that affect estrogen levels in the body are linked to an increased risk of breast cancer.

Body weight is an important example. Estrogen is produced in fat tissue. In general, more weight means more fat tissue and higher estrogen levels in postmenopausal women. This likely explains, at least in part, the increased breast cancer risk in women who are heavy after menopause.

Learn more about body weight and breast cancer risk. 

Blood estrogen levels and breast cancer before menopause

A pooled analysis of data from 7 studies found women with higher blood estrogen levels may have a modestly increased risk of breast cancer before menopause [69].

Studies in premenopausal women are challenging because estrogen levels vary over the menstrual cycle. For example, in the early phase of the menstrual cycle (follicular phase), estrogen levels are much lower than in the late phase (luteal phase).

Factors that affect blood estrogen levels

Blood estrogen levels are affected by many factors. Some of these are under your control.

Factors linked to lower estrogen levels in women include [22]:

• Maintaining a healthy weight after menopause
• Limiting alcohol intake
• Being physically active (getting exercise)

These steps may be linked to a decreased risk of breast cancer and other chronic diseases.

Taking menopausal hormone therapy (also called postmenopausal hormone therapy and hormone replacement therapy (HRT)) increases estrogen levels in the body.

Learn about other factors linked to the risk of breast cancer.

SUSAN G. KOMEN®‘S BREAST SELF-AWARENESS MESSAGES

1. Know your risk Talk with both sides of your family to learn about your family health history. Talk with a health care provider about your risk of breast cancer. 2. Get screened Talk with a health care provider about which screening tests are right for you if you’re at higher risk. Have a mammogram every year starting at age 40 if you’re at average risk.* Have a clinical breast exam at least every 3 years starting at age 25, and every year starting at age 40.* * Per National Comprehensive Cancer Network Guidelines 3. Know what is normal for you See a health care provider if you notice any of these breast changes: Lump, hard knot or thickening inside the breast or underarm area Swelling, warmth, redness or darkening of the breast Change in the size or shape of the breast Dimpling or puckering of the skin Itchy, scaly sore or rash on the nipple Pulling in of the nipple or other parts of the breast Nipple discharge that starts suddenly New pain in one spot that doesn’t go away To see illustrations of these warning signs, please visit the Warning Signs of Breast Cancer page. 4. Make healthy lifestyle choices Maintain a healthy weight. Make exercise part of your routine. Limit alcohol intake. Limit menopausal hormone therapy (postmenopausal hormone use). Breastfeed if you can.

Updated 12/16/24

This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.