HOW HORMONES AFFECT BREAST CANCER RISK Hormones are chemicals made by the body that control how cells and organs work. Estrogen is a female hormone made mainly in the ovaries. It’s important for sexual development and other body functions. From your first monthly period until menopause, estrogen stimulates normal breast cells. A higher lifetime exposure to estrogen may increase breast cancer risk. For example, your risk increases if you start your period at a young age or go through menopause at a later age. Other hormone-related risks are described below. Menopausal hormone therapy Pills Menopausal hormone therapy (MHT) is The U.S. Food and Drug Administration also known as postmenopausal hormone (FDA) recommends women use the lowest therapy and hormone replacement dose that eases symptoms for the shortest therapy. Many women use MHT pills to time needed. relieve hot flashes and other menopausal Any woman currently taking or thinking symptoms. MHT should be used at the Birth control about taking MHT pills should talk with her lowest dose and for the shortest time pills (oral doctor about the risks and benefits. contraceptives) needed to ease menopausal symptoms. Long-term use can increase breast cancer Vaginal creams, suppositories Current or recent use risk and other serious health conditions. and rings of birth control pills There are 2 main types of MHT pills: slightly increases breast Vaginal forms of MHT do not appear to cancer risk. However, estrogen plus progestin and estrogen increase the risk of breast cancer. However, this risk is quite small alone. if you’ve been diagnosed with breast cancer, vaginal estrogen rings and suppositories are because the risk of Estrogen plus progestin MHT breast cancer for most better than vaginal estrogen creams. Estrogen plus progestin MHT pills are young women is low used by women who still have a uterus. Patches Once a woman stops MHT pills increase breast cancer risk. Whether hormone patches affect breast taking the pill, her risk Once a woman stops taking them, her cancer risk is under study. goes down. Over time, risk goes down over time. this risk even goes Note: MHT is different from hormone away. Most studies have Estrogen alone MHT therapies used to treat breast cancer or looked at breast cancer Estrogen alone MHT pills are used by reduce risk (which act as “anti-hormone” risk with older, higher women who don’t have a uterus (have therapies). dose forms of the pill. had a hysterectomy). Some studies show The effects of lower- estrogen alone MHT pills may increase dose birth control pills breast cancer risk, but others don’t. More are still under study. research is needed. If you take birth control pills, talk with your doctor about its risks For more information, visit komen.org or call Susan G. Komen’s breast care helpline at and benefits. 1-877 GO KOMEN (1-877-465-6636) Monday through Friday, 9 AM to 10 PM ET. FACTS FOR LIFE HOW HORMONES AFFECT BREAST CANCER RISK Resources But what about... Susan G. Komen® the link between estrogen and Insulin-like growth factor 1 (IGF-1) is a 1-877 GO KOMEN breast cancer? natural hormone that plays a role in growth (1-877-465-6636) Some breast cancer cells need estrogen to komen.org and development. grow. When estrogen attaches to special proteins called estrogen receptors, the Studies have found higher levels of IGF-1 cancer cells with these receptors grow. in the blood may increase the risk of breast Estrogen receptor-positive breast cancers cancer. Measures of blood levels of IGF-1 Related have many cells with hormone receptors may one day help estimate breast cancer educational and can be treated with hormone therapy. risk. resources: women who have been diagnosed Prolactin is a hormone mainly produced • Risk Factors and Risk with breast cancer? Should they in the pituitary gland (a small gland Reduction avoid MHT? near the brain). It plays a role in breast • Breast Cancer & Risk MHT is not usually recommended for growth and the production of milk during breast cancer survivors because it may breastfeeding. Women with higher blood increase the risk of breast cancer recurrence levels of prolactin may have a higher risk of (the return of cancer) and cancer in the breast cancer than women with lower levels. opposite breast. Talk with your doctor Measures of prolactin blood levels may one about other ways to help ease menopausal day help estimate breast cancer risk. symptoms. Androgens (such as testosterone) are women with a family history of natural hormones that are important in breast cancer? sexual development. Higher amounts of It’s not clear whether or not women with a androgens in the blood may be linked to an family history of breast cancer should avoid increased risk of breast cancer in women. The list of resources is birth control pills or MHT. This topic is only a suggested resource under study. Talk with your doctor about and is not a complete listing of breast health and how your family history may affect your risk. breast cancer materials Use the family health history tool to record or information. The information contained and organize your family health history herein is not meant www.komen.org/FamilyHealth to be used for self- diagnosis or to replace the effects of natural hormones on the services of a medical professional. Komen does breast cancer? not endorse, recommend Estrogens are natural hormones that are or make any warranties or representations important in sexual development and regarding the accuracy, other body functions. Higher amounts completeness, timeliness, quality or non- of estrogen in the blood are linked to an infringement of any of increased risk of breast cancer in women the materials, products after menopause. Researchers are studying or information provided by the organizations a possible link to breast cancer before referenced herein. menopause. FACTS FOR LIFE The Running Ribbon is a registered trademark of Susan G. Komen®. Item No. KO0090 © 2019 Susan G. Komen® 7/ 1 9.