How To Learn About the Hormone Replacement Therapy Study

From 1991-2006, the National Institutes of Health ran the Women's Health Initiative (WHI), a long-term study that focused on strategies to prevent diseases that affect women.  The 15-year project involved more than 161,000 women from across the United States, aged 50-79.  As part of the Women's Health Initiative, a clinical trial testing the effects of hormone replacement therapy on heart disease, breast and colorectal cancer risk and osteoporotic fractures, was run.  Hormone therapy is the administration of either estrogen only or estrogen in combination with either progesterone or progestin (progesterone in synthetic form).  We have the Women's Health Initiative to thank for putting a stop to the routine practice of prescribing women hormone replacement therapy upon menopause. The information here (gleaned from the hormone therapy trial of the Women's Health Initiative) will help you better understand why:

  1. Hormone Therapy Trial Configuration  The hormone therapy clinical trial had two parts:  Post-menopausal women who took either estrogen plus progestin or a placebo and women who had undergone a hysterectomy and took either estrogen alone or a placebo.

  • Hormone Therapy Trial Stopped Early.  Both studies were to last through 2005 but both studies were stopped early-the estrogen-plus-progestin study in July 2002 and the estrogen-only study in February 2004.
  • Combination Study:  Increased Risk of Breast Cancer, Heart Attack, Blood Clots and Strokes.  The combination therapy study (estrogen plus progestin) was stopped due to results showing an increased risk of breast cancer and also increased risk for heart attack, blood clots and strokes.  Estrogen plus progestin did reduce the risk for hip and other fractures, and colorectal cancer. However, it was determined that the risks of using the hormones outweighed the benefits.

  • Estrogen-Only Study:  Increased Risk of Stroke and Venous Thrombosis.  The estrogen-only study was stopped because hormone therapy increased the risk of stroke and did not decrease the risk of coronary heart disease.  It also increased the risk for blood clots deep in a vein (venous thrombosis).   Estrogen alone also reduced the risk for hip and other fractures. 
  • Urinary Incontinence.  The WHI study also shows that both therapies-estrogen plus progestin and estrogen alone-increased the risk of developing urinary incontinence and worsened the symptoms of pre-existing incontinence.
  • Women's Health Initiative Memory Study.  An ancillary study called the WHI Memory Study found that women taking the combination therapy experienced twice the rate of dementia (including Alzheimer's disease) as those on the placebo.  Estrogen alone increased the risk of mild cognitive impairment. 
  • Women's Health Initiative Follow-Up.  The Women's Health Initiative will continue to follow women who were in the hormone replacement therapy trials until 2010.  This will help answer the question of how long the increased risks and benefits of hormone therapy last after stopping treatment.
  • Please discuss alternatives to hormone replacement therapy with your doctor; menopausal symptoms and osteoporosis can both be addressed through other means.


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