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Can Hormone Therapy Cause Cancer?

For many women going through menopause, the problematic hormonal changes involved can lead them to seek hormone replacement therapy (HRT). HRT involves taking hormones like estrogen and progestin to replenish hormone loss due to aging, for results like improved sleep, hot-flash and night-sweat prevention, and subdued mood swings.

A possible association between long-term use of HRT and breast cancer has been shown in numerous studies, however.

The authors of a study in the Journal of the American Medical Association determined the link between HRT use over a five-year period and incidence of breast cancer. Over 700 postmenopausal women 50-74 years old with breast cancer, and nearly as many healthy women, were evaluated for hormone usage.

Overall, breast cancer was 60-85% more likely in women who had used HRT both recently and long-term. HRT use over multiple years and combination therapy of both estrogen and progestin increased risk of one type of breast cancer even more substantially. Continuous long-term and combined-hormone therapy increased lobular breast cancer (a specific type of breast cancer) risk six times.

HRT use also increased risk for nonlobular breast cancer (a more common form). If that isn't enough information to scare you away from hormone therapy, you might be interested to know that other possible side effects include acne; weight gain; increased facial hair; high blood pressure; depression; and heart attacks.


Chen CL, Weiss NS, Newcomb P, et al. Hormone replacement therapy in relation to breast cancer. Journal of the American Medical Association 2002:287(6), pp. 734-741.

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