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The Women’s Health Initiative study suggested that HRT increased the risk of breast cancer, blood clots, and stroke, but it also may lower the risk of colorectal cancer and fractures.
In 2002, the Women’s Health Initiative study, commonly referred to as WHI, revealed that combined estrogen and progestin hormone replacement therapy not only increased the risk of serious health problems, but it provided no protection against heart disease—one of the reasons women were taking the drug on a long-term basis. In fact, figures showed HRT increased the risk of heart attack by 29 percent.
Since then, women and their doctors have been more concerned about the risks of HRT than its benefits—some of which include decreased risk of colorectal cancer, protection against osteoporosis-related hip fractures, and reduction in the frequency and severity of menopausal symptoms, such as hot flashes.
The risks of HRT, however, are hard to ignore. WHI participants on combined HRT had a 26 percent higher relative risk for breast cancer, a 41 percent increased relative risk of stroke, and a doubled relative risk of blood clots (see table for absolute risk amounts). For estrogen-alone HRT, women face a higher risk of stroke, and because of the increased risk for endometrial cancer, it can only be given to women who have had hysterectomies.
View Chart: Relative & Absolute Risk with HRT
Five years after the WHI results were first published, a second analysis presented earlier this year in the Journal of the American Medical Association reported new findings surrounding some of the adverse effects. The re-analysis of the estrogen-alone HRT group saw a decreased risk of heart disease in women under 60. However, WHI officials noted the study included few women under 55—the average age in the study was 63—so the findings are not considered statistically significant according to research standards, meaning the decrease could have occurred by chance. Data showed that combined HRT either had no effect on heart disease or increased the risk based on age, confirming findings from the 2002 WHI analysis.
The National Institutes of Health, sponsor of the WHI study, stands by its recommendation against long-term use of HRT to protect against heart disease. Women in need of lowering their risk of heart disease can look to a class of drugs used to lower cholesterol called statins that have been found to be as effective as HRT and carry fewer risks. Other therapeutic options for bone health and breast and colorectal cancer prevention are also available and pose fewer or less serious risks, including bisphosphonates to strengthen bone tissue, regular screening for breast and colorectal cancers, and selective estrogen receptor modulators, such as tamoxifen and Evista (raloxifene), to prevent breast cancer.
Some of the effects analyzed in the WHI study and the corresponding risk or benefit are detailed below for the estrogen plus progestin group compared with placebo.