The FDA Reverses Itself on Estrogen, But Why Did It Take 20 Years?

For more than two decades, the Food and Drug Administration (FDA) told women that estrogen increases the risk of breast cancer. Definitively.

Doctors (including me, for a while) repeated this. It was amplified in headlines. Hormone replacement – once widely prescribed – became rare.

That all changed on November 10, 2025. The FDA commissioner not only announced the removal of the breast cancer warning on estrogen products but also stated outright that this false warning was “one of the biggest mistakes in modern medicine.” He cited research well-known in my field that hormone replacement in women dramatically reduces health risks, including heart attacks, strokes, fractures, and dementia. An entire generation of women was needlessly scared away from hormone replacement, and their enjoyment of life and their health outcomes suffered because of it.

So, the obvious question is: why didn’t we know this 20 years ago? The uncomfortable answer is that, in some ways, we did.

Making Headlines

When results from the Women’s Health Initiative (WHI) national study were released in 2002, the headlines were dramatic: Hormones cause breast cancer and heart disease. Prescriptions plummeted almost overnight. Millions of women stopped therapy immediately. Many of my patients suffered that sudden misery.

What received far less attention were the limitations of the research. The population that was studied was older than typical menopause patients. The formulation included synthetic progestins. And within just a few years, reanalysis of the same data revealed something very different: Women who began hormone therapy closer to menopause had reduced cardiovascular risk, and women using estrogen without synthetic progestins did not have increased breast cancer risk. Rather, some analyses even suggested a risk reduction.

But it was already too late. Patients remember headlines. Once a message like hormones cause cancer becomes embedded in public consciousness, reversing it is extraordinarily difficult. Women knew about it, and so did their doctors. Hormone therapy went from about 30 percent of menopausal women to about one percent. Osteoporotic fractures increased. Millions of women suffered symptoms like hot flashes, sleep disruption, mood changes, sexual dysfunction, and rapid bone loss. Many women entering menopause were told to “just live with it.”

Reversing Course

As a physician focused on optimizing health span, I see this as a tragedy hiding in plain sight. Menopause is, biologically speaking, a hormone deficiency syndrome. When women lose hormones their tissues rely on, those tissues begin to deteriorate – in the cardiovascular system, brain, bones, and genitourinary tract. This is well-known. Yet an entire generation was told that replacing their natural hormones was inherently dangerous.

For women, the 50s are a critical window of time for prevention of serious health issues. Because of the WHI study, rates of fractures, heart attacks, strokes, and dementia are certainly higher than they should have been. Beyond that has been the quieter suffering: urinary complaints, sexual dysfunction, loss of energy, poor sleep, and brain fog. How many women stepped back from careers because they felt like they “couldn’t bring it?” How many relationships were strained? And most importantly – how many lives were shortened?

This is not about villainy; I’m not calling for abandoning regulatory oversight. But we need to be open about the losses society has experienced from “one of the biggest mistakes in modern medicine” and demand some humility from the regulatory agencies and research organizations at the core of this system.

Scientific consensus at regulatory agencies such as the FDA often amounts to a show of hands around a table – not really the eternal truth it’s made out to be. We need to build a system that responds faster when evidence changes, so women don’t have to wait another generation to fully enjoy the second half of their lives.

Gustav Lo, MD, is the Chief Medical Officer of RegenCen, a regenerative and anti-aging medical clinic specializing in hormone replacement and longevity medicine. RegenCen is a Menopause Society Certified Practitioner and has multiple locations in Florida, including Lake Mary and Winter Park.