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Menopausal Hormone Replacement Therapy

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Menopausal hormone use (sometimes referred to as hormone replacement therapy or HRT) usually involves treatment with either estrogen alone or a combination of estrogen with progesterone or progestin, a synthetic hormone with effects similar to those of progesterone.

The best evidence for the risks and benefits of menopausal hormone replacement therapy comes from the Women's Health Initiative (WHI), a large randomized clinical trial including more than 16,000 healthy women, sponsored by the National Institutes of Health (NIH).

Results from the trial published in 2002 showed that the overall risks of estrogen plus progestin outweigh the benefits. Among the risks observed after 5.6 years of follow-up were increased risks of breast cancer, heart disease, stroke and blood clots.

On March 1, 2004, after nearly seven years of follow-up, NIH stopped the estrogen-alone arm of the trial, concluding that estrogen alone does not appear to affect (either increase or decrease) heart disease, a key question of the study. In addition, estrogen alone appears to increase the risk of stroke and decrease the risk of hip fracture. No increase in breast cancer risk was observed during the study period.