 We've known about the role of estrogen in breast cancer, going back to the 1800s, when in some cases surgical removal of the ovaries seemed to help. Ovaries were said to send out mysterious influences to the rest of the body, which in 1923 we identified as estrogen. The medical profession jumped on this discovery and started injecting menopausal women by the thousands, shots that gave a respectable hook on which to hang visits to the doctor. Soon there were pills and patches, and medical journals like the Journal of the American Medical Association regaled doctors with ads on how they can help women to happiness by prescribing estrogen. You could turn this into that. Or when women outlived their ovaries, there was premarin. As far back as the 40s, concerns were raised that this practice might cause breast cancer, noting it would have been nice to figure this out first before we started dosing women en masse. But breast cancer risk didn't matter because heart disease is the number one killer of women, concluded reviews, and because women taking hormones appeared to have lower heart attack rates that would outweigh the extra breast cancer. But women taking estrogen tended to be of higher socioeconomic class, tended to exercise more and engage in other healthy lifestyle changes, like increased fiber intake and getting their cholesterol checked. So maybe that's why women taking estrogens appeared to be protected from heart disease. Maybe it had nothing to do with the drugs themselves, despite the medical profession's enthusiasm for the stuff Only a randomized clinical trial could really resolve this question. You split women into two groups, half get the hormones, half get a placebo, and you follow them out for a few years. But there was no such study until the 1990s, when the Women's Health Initiative study was designed. Wait a second. Why did it take the bulk of a century to decide to definitively study the safety of something that prescribed to millions of women? Maybe it's because there had never been a female director of the National Institutes of Health until then. Just three weeks after being named NIH director, she went before Congress to announce we need a moonwalk for women, and that moonwalk took the form of the Women's Health Initiative study. The bombshell landed. Summer 2002 there was so much more invasive breast cancer in the hormone users that they were forced to stop the study prematurely. Yeah, but what about heart disease? Wasn't that supposed to balance things out? The women didn't just have more breast cancer. They had more heart attacks, more strokes, more blood clots to their lungs. The news that women treated with hormone replacement therapy experienced higher rates of breast cancer, and cardiovascular disease and overall harm rocked women and physicians across the country. Estrogens started out as the most prescribed drug in America before the study, but the number of prescriptions dropped immediately, and within a year so did the incidence of breast cancer in the United States. Here's the data from California, a nice drop-off in the rate of invasive breast cancer. But the most important part of this story was why were we all so surprised? There had been decade after decade of repeated warnings about the risks of cancer. In fact, the reason breast cancer patients had so much trouble suing the drug company was that the drugs contained warning labels for decades, and having disclosed it, surely any reasonable physician would have included it in their risk and benefit discussion with their patients. It's like the warning labels on packs of cigarettes. If you get lung cancer now, you should have known better. And so if you got breast cancer, don't blame the drug company. They warned you about the risks right there, a clearest day. Why didn't more doctors warn their patients? Even after the study came out, millions of prescriptions continued to be dispensed. That's a lot of cancer in our patients we caused, wrote one doctor. How long will it take us to stop listening to the drug companies and admit that we're harming many of our patients and start changing our prescription habits? Why did this practice continue in the face of mounting evidence of harm? Well, it is a multi-billion dollar industry. Despite an overwhelming amount of evidence to the contrary, many physicians still believe that estrogenic hormones have overall health benefits. A non-evidence-based perception that may be the result of decades of carefully orchestrated corporate influence on the medical literature. Dozens of ghost-written reviews were published in medical journals to promote unproven benefits and downplay the harms of menopausal hormone therapy. They'd pay PR companies to write the articles and then pass them off as written by some expert. So gynecologists must switch allegiance from eminence-based to evidence-based medicine. Consider what the science actually says and not just what some so-called expert says. One might say the current culture of gynecology encourages the dissemination of health advice based on advertising rather than science. Women were placed in the way of harm by their physicians who acted as unsuspecting patsies for the pharmaceutical companies. If we really wanted to prevent heart attacks in women, simple lifestyle behaviors can eliminate more than 90% of heart attack risk. So instead of being big farmers pawns, recommending a healthful diet, increased exercise, and smoking cessation would truly benefit women's health.