On July 17th, 2002, women across the country and the world woke up to some very interesting news. The estrogen plus progestin (hormone replacement therapy, HRT) study of the Women’s Health Initiative (WHI) was stopped early because of an unacceptable number of adverse events. The results on HRT from the WHI are very informative, as they finally clear up some very important questions.

Currently, HRT is the 2nd most widely prescribed drug in the US (so it has the potential to benefit or harm many women). Given that there seemed to be both benefits and risks for HRT, the National Institutes of Health began a research study among a large group of ethnically diverse women to assess the cumulative benefits and/or risks of taking HRT. Between 1993 and 1998, the WHI enrolled 161,809 postmenopausal women between the ages of 50 and 79. This is a massive study. These women were then funneled into one of several studies (all of which are continuing, with the exception of the HRT wing).

The HRT study had over 16,000 women enrolled, and the scientists were to follow them for about 8.5 years. But in the spring of both 2000 and 2001, something happened. An outside safety board observed an increased number of cardiovascular events and an increase in a global health index (cumulative score or 7 different health events) of adverse events. At that time, the adverse events weren’t high enough to stop the trial. But on May 31, 2002, the safety board found that the adverse effects in heart disease, stroke, breast cancer, deep vein thrombosis, pulmonary embolism, and the global health index were high enough that the risks of taking HRT significantly outweighed the benefits. The trial was stopped, having followed the women for about 5.2 rather than 8.5 years.

While some benefits were observed in the HRT group-a decrease in fractures and colorectal cancer-these benefits were not significant enough to override the increased risks (and there are other FDA approved medications for osteoporosis). An accompanying editorial in JAMA stated, “the whole purpose of healthy women taking long-term estrogen/progestin therapy is to preserve health and prevent disease. The results of this study provide strong evidence that the opposite is happening for important aspects of women’s health, even if the absolute risk is low”. They further go on to end the editorial with, “the WHI provides an important health answer for generations of healthy postmenopausal women to come-do not use estrogen/progestin to prevent chronic disease.”

While this study does answer several important questions, it doesn’t answer others. It doesn’t answer whether even short term (less than 1 year) use of HRT for the treatment of hot flashes and other menopausal symptoms has risks. It also doesn’t answer whether estrogen therapy without progestin has elevated risks (for those women who don’t have a uterus). These results will be available from the WHI in a few years.

For now, if you are taking HRT or estrogen or are considering taking them, I suggest that you talk with your doctor.