Why Is Hormone Replacement Therapy So Controversial?

Every year, more than a million women enter menopause. While some women sail through this phase of their lives with minimal trouble, many if not most suffer with hot flashes, night sweats and other symptoms. Doctors may offer them hormone replacement therapy, but this treatment has long been controversial. Does it increase the risk for breast cancer?

Is There a Link Between Hormone Therapy and Breast Cancer:

For decades, hormone replacement therapy was considered the standard of care for menopausal women. It certainly eased hot flashes. Doctors though it could also reduce the risk of heart disease and brittle bones.

Then along came the Women’s Health Initiative (WHI), a large, long-term clinical trial of estrogen and progestin therapy. It demonstrated an association between hormone therapy and an increased risk for breast cancer, blood clots and heart attacks. In subsequent years, however, some scientists have criticized both the methodology and the conclusions of the WHI.

Bringing the Research Up to Date:

By now, the WHI is old news. It began in 1991 and concluded in 2005. The primary findings were published in 2002. Nonetheless, scientists are still studying possible links between hormones and breast cancer. What have we learned in the past two decades?

A study of menopausal hormonal therapy published in JAMA Network Open examined the risk of estrogen and progestin in the later development of breast cancer (JAMA Network Open, June 23, 2025). The authors reviewed data from 31 studies involving over 42,000 women with breast cancer and more than 71,000 control participants. Healthy weight women taking this kind of hormone therapy were more likely to be diagnosed with specific breast cancer subtypes known as luminal A and luminal B. The association of menopausal hormone therapy and these specific types of tumor was less marked in heavier women.

A different study, a meta-analysis published in Lancet Oncology, analyzed data from more than 450,000 women under 55 (Lancet Oncology, July 2025). These women were taking hormone replacement therapy, either estrogen alone or estrogen plus progestin, to help with perimenopause or following a hysterectomy. Nearly 8,500 of these women developed breast cancer before they turned 55. According to the analysis, use of estrogen alone by  women following hysterectomy decreased the risk of young-onset breast cancer. Use of estrogen plus progestin increased the likelihood by 10 percent.

Hormone Replacement Therapy for Menopause:

Millions of women still wonder whether or not they should take hormones to help their hot flashes. We received this testimonial several years ago.

Q. I have been on Premarin for 26 years with no problems whatsoever. Without it, I prayed to die because of the horrendous effects of menopause.

I am also on two compounded products, testosterone/DHEA cream and progesterone cream. Based on my own experience, I believe all women should take advantage of hormone replacement for longevity and a good healthy life after menopause. I look and feel great at my age of 69 years.

History of the Controversy:

A. Until 2002, many doctors thought that most postmenopausal women should be taking estrogen. (Women who still had a uterus were also supposed to take progesterone to prevent endometrial cancer.) They believed that hormone replacement therapy (HRT) would prevent chronic diseases, especially heart attacks, strokes, osteoporosis and even Alzheimer’s disease.

Then, fifteen years ago, the results of the Women’s Health Initiative were published (JAMA, July 17, 2002).  This randomized controlled trial showed that “Overall health risks exceeded benefits” when estrogen and progesterone (Prempro) for five years was compared to placebo. Another group of women took Premarin (estrogen) alone or placebo for seven years.

What the WHI Showed:

Women on HRT had a higher risk of strokes and breast cancer (JAMA, Oct.2, 2013). During the five-year duration of the study, however, there was no difference in mortality between women taking HRT and those taking placebo. Another report showed that after 18 years the participants still had no significant differences in mortality (JAMA, Sep. 12, 2017).

Women like you who suffer during menopause often feel more comfortable taking estrogen (and progesterone, if indicated) during the time they need to suppress hot flashes. Experts usually recommend the lowest effective dose for the shortest possible time. In most cases, that would be considerably less than 26 years.

Other Objections to Premarin:

Some women object to Premarin and Prempro on ethical grounds. Premarin is made from pregnant mares’ urine. Many people worry that keeping the horses pregnant and confined constitutes inhumane treatment. Doctors can prescribe other forms of HRT such as estradiol. Consequently, women who object to Premarin should request an alternative if they need the relief from hormone therapy.