A headline from 2002is still deciding your care.

What happened

In July 2002 the Women’s Health Initiative stopped one arm of a large trial early and reported that combined oestrogen-plus-progestin therapy raised the risk of breast cancer, stroke and blood clots. It was front-page news everywhere. Prescriptions in the United States fell by roughly half within a year and kept falling for a decade.

Millions of women stopped treatment, and millions more were never offered it. An entire cohort of physicians trained in the years that followed learned to treat hormone therapy as something to avoid rather than something to weigh.

Why it did not mean what it was taken to mean

The trial was not designed to answer the question women were asking. It was testing whether hormone therapy prevented chronic disease in older women, not whether it safely relieved symptoms at the time of menopause. The average participant was sixty-three years old and more than a decade past her final period. Two-thirds were sixty or over.

The result was then applied to forty-eight-year-olds who had not slept properly in two years — a group the trial barely contained. Starting hormone therapy at fifty and starting it at sixty-five are different interventions with different risk profiles, and the reporting collapsed the two.

What the evidence supports now

The second arm of the same trial, in women who had had a hysterectomy and so took oestrogen alone, found no increase in breast cancer. In long-term follow-up, incidence in that group was lower than in the women taking placebo. The breast cancer signal was specific to the combined regimen.

For combined therapy the increase is real, and it is small: on the order of fewer than one additional case per thousand women per year of use. That is a number you are entitled to have in front of you rather than a category you are told to avoid.

The major menopause and obstetric societies have since converged on the same position. For a healthy woman under sixty, or within ten years of her final period, the benefits of hormone therapy for troublesome flashes and night sweats generally outweigh the risks. That is the current mainstream view, not a contrarian one.

What we are not saying

That it is safe for everyone, or that you should be on it. The risk is genuine, it rises with age and with time since menopause, and some histories rule it out entirely. The next section is the list of those histories, and we would rather you read it than skip it.