Hormone replacement therapy was fairly common until 2002, when an NIH study, the Women’s Health Initiative, upended the field. The investigators found that hormone replacement therapy raised the risk of breast cancer, after which they stopped the study and women around the nation suddenly stopped taking estrogen.
Yet the research was flawed—most notably because the participants were primarily older women—and many have since critiqued the methodology and conclusion. In addition to alleviating the sometimes-debilitating symptoms of menopause, estrogen has protective qualities such as defending against heart attacks, osteoporosis, and dementia. The decision will be different for everyone, but many doctors believe that estrogen is not only safe but helps prevent other health problems.