Dr. JoAnn Manson is one of the principal investigators for the landmark Women's Health Initiiative study.

In the past decade, the Women’s Health Initiative (WHI) Hormone Therapy Trial, for which Brigham and Women’s Hospital was one of the centers,  has revealed much about the benefits and risks associated with hormone therapy for menopausal women and has changed the way women around the world manage their symptoms.

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,” wrote JoAnn Manson, MD, MPH, DrPH, BWH Chief, Division of Preventive Medicine and one of the principal investigators of the WHI, in a co-authored editorial for the medical journal, Menopause. “In fact, these women did not have a reduced risk of heart disease from hormone therapy and may even have suffered harm.”

Dr. Manson said 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, Dr. Manson believes that it will be important to understand whether different types and formulations of hormone therapy, such as patches, bio-identical 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 Dr. Manson. “The ‘one size fits all’ approach to decision-making is no longer acceptable.”

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 composed of several clinical trials, two of which were the Hormone Therapy Trials.


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