How One Flawed Study Scared Women Away From HRT & Set Women's Health Back Decades 

At least one in four women utilized hormone replacement therapy (HRT) in 1997. This popular treatment empowered women to take charge of their health by counteracting fluctuating hormone levels and the decline of estrogen, progesterone, and testosterone that occurs during menopause. (Yep, the same decline responsible for menopause symptoms like weight gain, hot flashes, night sweats, and disrupted sleep). 

By 2020, the number of women using HRT plummeted to just 5%1. This steep dip didn’t occur because women suddenly stopped experiencing menopausal symptoms or because HRT became less effective. In fact, HRT has only become more advanced and personalized with options for  bioidentical hormones.

Rather many experts agree the decline can be tied to a 2002 Women’s Health Initiative study2 that linked HRT to an increased risk of breast cancer. 

“The big challenge goes back to 2002, when the Women’s Health Initiative came out. It was a huge study that got a ton of attention,” explains functional medicine physician Wendie Trubow, M.D., MBA. 

When published, it terrified an entire generation of women and physicians. Headlines screamed warnings about breast cancer, blood clots, and strokes. Healthcare professionals stopped prescribing HRT, and women who had been managing their symptoms successfully were told to quit cold turkey.

The Women's Health Initiative was designed to be groundbreaking. Researchers wanted to understand whether hormone therapy impacted cardiovascular disease or breast and colorectal cancer risk in postmenopausal women. 

But the study was poorly constructed from the start. Board-certified OB/GYN and menopause specialist Jila Senemar, MD, FACOG, shared on the mindbodygreen podcast that the biggest issue was how the study was conducted. 

“The qualifications to be part of the study were a big factor,” says Senemar. It enrolled women with an average age of 63, many of whom were a decade or more past menopause (note: menopause is defined as going one full year without a menstrual cycle).  

However, most women start HRT in their early 50s, right around menopause, when symptoms are most severe and when the protective effects of estrogen or testosterone are most pronounced. 

What’s more, women were given conjugated equine estrogens (CEE) and medroxyprogesterone acetate (MPA)—two forms of hormone therapy no longer in use today. 

“Most of us don’t use synthetic hormones anymore,” longevity and regenerative medicine physician Amy Killen, M.D. explained on the mindbodygreen podcast. Instead, modern HRT opts for bioidentical or body identical hormones that “essentially match the same hormone chemical structure that your body makes.” 

Not only did the WHI study focus on the wrong demographics at the wrong stage of life with the wrong product—but the conclusions drawn from the study were misrepresented.

The 2002 WHI study found small but statistically significant increases in certain health risks among women taking combined hormone therapy (E+P): specifically, an increased risk of invasive breast cancer (8 additional cases per 10,000 women per year), coronary heart disease, stroke, and pulmonary embolism. 

The absolute risks were relatively small—for example, the breast cancer finding translated to roughly one additional case per 1,000 women per year. What’s more, the study also showed the potential benefits of HRT therapy.

“In the estrogen-only arm, we actually did notice a decrease in the development of breast cancer,” says Senemar. Plus, the study found links between HRT and a reduced risk of colorectal cancer and hip fracture. 

But, the reporting of the results in the study and the coverage of the study focused almost exclusively on the cancer and cardiovascular risks, and the nuanced context about timing, age, and formulation was lost (another flaw). The negative message about HRT was so prevalent that many women today still believe HRT causes cancer. 

As Trubow sums it up: "Repeat studies show hormones protect your colon, brain, and heart—not to mention your skin, sense of vitality, sex drive, and ability to have sex." 

It’s a sentiment backed by other experts, like Killian, who deems HRT the “best thing you can do to improve long-term health and longevity” outside of lifestyle optimizations. 

If you're considering HRT or wondering if you should have stayed on it, the most important thing is to have an informed conversation with your doctor. 

The sharp drop in HRT use wasn't based on sound science. It was fueled by a flawed study and sensationalized headlines. But for many women, hormone replacement therapy is not only safe but life-changing.