The Women’s Health Initiative is one of the largest studies ever done on hormone therapy for women after menopause. Researchers looked at decades of data to understand when hormone therapy helps and when it might cause problems. The big takeaway? Timing matters a lot. Starting hormone therapy early in menopause appears to protect bones and may help the heart, but starting it later in life seems to increase certain risks. The type of hormone therapy also makes a difference—some versions increase breast cancer risk while others don’t. This research helps doctors and women make better decisions about whether hormone therapy is right for them.

The Quick Take

  • What they studied: Whether hormone therapy after menopause helps or hurts women’s health, including effects on bones, heart, cancer risk, and brain function
  • Who participated: This review analyzed data from the Women’s Health Initiative, a massive research project that followed thousands of postmenopausal women over many years
  • Key finding: The timing of when women start hormone therapy is crucial—starting early (before age 60 or within 10 years of menopause) appears safer and more beneficial than starting later in life
  • What it means for you: If you’re considering hormone therapy for menopause symptoms, talk with your doctor about when you start it. Starting earlier may offer more benefits with fewer risks, but this depends on your personal health history and what symptoms you’re experiencing

The Research Details

This is a narrative review, which means researchers carefully read and summarized findings from many different studies about hormone therapy. They searched medical databases for studies published in English that looked at hormone therapy’s effects on bones, heart health, metabolism, cancer, and brain function. They included both large clinical trials (where some women got hormone therapy and others didn’t) and observational studies (where researchers tracked women who chose to take hormone therapy). By combining all this information, they created a comprehensive picture of what we know about hormone therapy’s effects.

A narrative review is valuable because it pulls together decades of research into one place, helping doctors and patients understand the big picture. The Women’s Health Initiative studies are especially important because they followed real women over many years and measured actual health outcomes, not just what happened in a lab. This type of research is considered very reliable for understanding how treatments affect people in real life.

This review is based on data from the Women’s Health Initiative, which is considered one of the most rigorous and important health studies ever conducted. The researchers used systematic methods to find and evaluate studies, which makes their conclusions more trustworthy. However, because this is a review of other studies rather than a new experiment, the strength of conclusions depends on the quality of the original research they reviewed.

What the Results Show

The research shows that hormone therapy has very different effects depending on when women start taking it. For bones, the news is consistently good: both types of hormone therapy tested (combined estrogen-progestin and estrogen-only) significantly reduced fractures in the hip, spine, and other bones. This protection was even stronger when women also took calcium and vitamin D supplements. For heart health, timing is everything. Women who started hormone therapy before age 60 or within 10 years of menopause showed potential heart benefits. However, women who started hormone therapy at age 65 or older had increased risks of heart attacks and strokes. This finding supports what scientists call the ‘window of opportunity’—a specific time period when hormone therapy is most likely to help rather than harm.

For cancer risk, the picture is mixed and depends on the type of hormone therapy. Combined hormone therapy (estrogen plus progestin) increased the risk of invasive breast cancer, especially in women who had used it before. Estrogen-only therapy showed no significant increase in breast cancer risk. Both types of hormone therapy lowered the risk of colorectal cancer during the time women were actively taking it. For brain health, early hormone therapy use (starting soon after menopause) had no effect on thinking and memory problems. However, starting hormone therapy late in life (at age 65 or older) was associated with increased dementia risk.

These findings build on decades of hormone therapy research and help clarify confusing earlier results. The Women’s Health Initiative was groundbreaking because it provided clear answers to questions that had been debated for years. These results now guide how doctors recommend hormone therapy and have changed clinical practice significantly. The emphasis on timing as a crucial factor is one of the most important insights from this research.

This review summarizes other studies rather than conducting new research, so its conclusions depend on the quality of those original studies. The Women’s Health Initiative focused mainly on one type of hormone therapy (conjugated equine estrogen), so results may not apply to all the different hormone therapy options available today. Individual women’s experiences can vary based on their personal health history, genetics, and other factors. The studies were conducted over many years, and medical knowledge and treatments have continued to evolve.

The Bottom Line

If you’re considering hormone therapy for menopause symptoms, discuss timing with your doctor. Starting hormone therapy early in menopause (before age 60 or within 10 years of menopause onset) appears to offer more benefits than risks for most women. Starting after age 65 carries increased risks that may outweigh benefits. The type of hormone therapy matters—combined estrogen-progestin therapy carries higher breast cancer risk than estrogen-only therapy. These recommendations should be personalized based on your individual health history, family history of cancer and heart disease, and severity of menopause symptoms. Confidence level: High for bone health benefits and timing effects on heart health; Moderate for cancer risk differences.

Women experiencing moderate to severe menopause symptoms who are considering hormone therapy should pay close attention to these findings. Women in their 50s and early 60s may find hormone therapy particularly helpful. Women over 65 should be especially cautious and discuss risks carefully with their doctors. Women with a personal or strong family history of breast cancer should discuss hormone therapy options thoroughly with their healthcare provider. Men and women who haven’t gone through menopause don’t need to apply these findings to themselves right now, but may find them useful in the future.

Benefits like bone protection can develop within the first year or two of hormone therapy use. Heart health benefits or risks may take several years to become apparent. Cancer risk changes typically emerge after several years of use. Brain health effects may take years to develop. Most women notice improvement in menopause symptoms like hot flashes within weeks to a few months of starting hormone therapy.

Want to Apply This Research?

  • Track menopause symptoms (hot flashes, night sweats, mood changes) weekly on a scale of 1-10, along with any side effects or concerns. Note the date you start or stop hormone therapy to correlate with symptom changes.
  • If starting hormone therapy, set a reminder to take it at the same time each day. Schedule follow-up appointments with your doctor at 3 months, 6 months, and annually to reassess whether the therapy is still right for you and to monitor for any side effects.
  • Create a long-term health tracking system that includes: menopause symptom severity, any new health concerns, medication changes, and annual check-in dates with your healthcare provider. Use the app to set reminders for bone health screenings and cancer screenings as recommended by your doctor based on your age and risk factors.

This summary is based on a review of research about hormone therapy for menopause and is intended for educational purposes only. It is not medical advice. Decisions about hormone therapy are highly individual and depend on your personal health history, symptoms, and risk factors. You should not start, stop, or change hormone therapy based on this information alone. Always consult with your healthcare provider or gynecologist before making any decisions about hormone therapy. Your doctor can help you weigh the specific benefits and risks for your situation and discuss all available treatment options for menopause symptoms.