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Menopausal hormone therapy and the risk of breast cancer

Wendy Y Chen, MD, MPH
Section Editors
Robert L Barbieri, MD
William F Crowley, Jr, MD
Joann G Elmore, MD, MPH
Deputy Editor
Kathryn A Martin, MD


One of the greatest concerns of women who are considering menopausal hormone therapy (MHT) is the relationship between hormone use and breast cancer. The results of the Women's Health Initiative (WHI) trial of combined estrogen-progestin, a large randomized, controlled trial, are consistent with the increased risk of breast cancer seen in many observational studies of MHT. (See 'Women's Health Initiative' below.)

Observational studies of MHT and breast cancer and the results from the WHI will be reviewed here. The relationship between endogenous hormones and breast cancer and a general discussion of the risks and benefits of MHT are discussed separately. (See "Factors that modify breast cancer risk in women" and "Menopausal hormone therapy: Benefits and risks".)


Support for the association of menopausal hormone therapy (MHT) with breast cancer is derived from studies that suggest that prolonged exposure to higher concentrations of endogenous estrogen increases the risk of breast cancer. These risk factors include:

Reproductive factors, including age at menarche, age at first live birth, age at menopause, and possibly parity and breast feeding.

Higher serum estrogen concentrations in postmenopausal women. The association is less clear in premenopausal women.

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Literature review current through: Nov 2017. | This topic last updated: Mar 07, 2016.
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