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This year marks the decade anniversary of the Women's Health Initiative (WHI) Hormone Therapy Trial report. Launched in the early 1990s, WHI was the largest women's health research program in the nation, and it focused on addressing the most common causes of death, disability and poor quality of life in postmenopausal women. The program was comprised of several clinical trials, two of which were the Hormone Therapy Trials (estrogen plus progestin and estrogen-alone) and an observational study.
In recognition of the milestone, JoAnn Manson, MD, MPH, DrPH, BWH chief of the Division of Preventive Medicine and one of the principal investigators of the WHI, co-authored an editorial for the medical journal, Menopause.
In the editorial, Manson, who is also the Michael and Lee Bell Professor of Women's Health at Harvard Medical School and the current president of the North American Menopause Society, discusses the epic study that changed clinical practice and beliefs about hormone therapy for menopause management.
The findings from the hormone trial that included estrogen plus progestin were monumental in demonstrating a link between hormone therapy and increased risks of heart disease, stroke, pulmonary embolism and breast cancer in postmenopausal women. The trial was initially designed to assess the role of hormone therapy in the prevention of heart disease and chronic diseases. During the trial, the researchers discovered that overall risks of hormone therapy exceeded benefits, especially for older women in the study. Given this, the two hormone therapy trials ended early to protect study participants.
The estrogen plus progestin trial was stopped three years early because the risks clearly outweighed the benefits. The estrogen-alone trial (for women with hysterectomy) showed fewer risks but was stopped one year early due to an increased risk of stroke.
"The WHI deserves credit for stopping the growing clinical practice of prescribing hormone therapy to older women who were at very high risk of heart disease," said Manson. "In fact, these women did not have a reduced risk of heart disease from hormone therapy and may even have suffered harm."
Looking to the Future
Manson states that although the researchers observed health risks mostly in older menopausal women, doctors ceased hormone therapy for all women with menopause. This included newly menopausal, healthy women who tended to benefit from hormone therapy for symptom management and had low rates of adverse events. As a result, prescriptions for hormone therapy plummeted for women in all age groups.
Over the past 10 years, research from the WHI and other studies have suggested that younger women closer to the onset of menopause tend to have better outcomes on hormone therapy than older women further along in menopause. Since younger women are also more likely to have hot flashes and other menopausal symptoms, hormone therapy may improve their symptoms and quality of life and have a favorable benefit-risk ratio. This seems to be especially true for estrogen-alone, which showed favorable results for both heart disease and all-cause mortality in younger women.
Looking to the future, Manson believes that it will be important to understand whether different types and formulations of hormone therapy, such as patches, bioidentical products or lower doses of hormones will have a different balance of benefits and risks.
"The recent findings highlight the importance of individualized care for women," said Manson. "The ‘one size fits all' approach to decision-making is no longer acceptable."