A recent study conducted by researchers at the National Institutes of Health (NIH) suggests that hormone therapy can influence breast cancer risk in women younger than 55. The study examined two widely used forms of hormone therapy and discovered that each one impacts the risk of developing breast cancer differently.
Hormone therapy is often given to women to ease menopause symptoms or after surgery to remove the uterus or ovaries. The two main types of therapy studied were:
- E-HT (estrogen-only hormone therapy)
- EP-HT (estrogen plus progestin hormone therapy)
Result of Study
Women who used estrogen-only hormone therapy (E-HT) had a 14% lower risk of developing breast cancer. This is compared to women who had never used hormone therapy. This lower risk was even stronger in women who started using it at a younger age or used it for a longer time. However, E-HT is usually only given to women who have had their uterus removed (a hysterectomy) because it can increase the risk of cancer in the uterus.
On the other hand, women who used EP-HT had a 10% higher risk of developing breast cancer. Women who used EP-HT for over two years faced an 18% increase in risk, particularly those who retained both their uterus and ovaries. This suggests that whether a woman has had surgery to remove these organs may affect her breast cancer risk while on hormone therapy.
Expert Opinions
Dr. Katie O’Brien, who led the study at the NIH’s National Institute of Environmental Health Sciences (NIEHS), said, “Hormone therapy can really help many women feel better. Our findings give women and doctors more information to make the best choices for their health.”
The study looked at health data from more than 459,000 women under 55 from many countries including the U.S., Europe, Asia and Australia. It’s one of the biggest studies focused on younger women and hormone therapy.
Breast Cancer Risk Estimates
Here’s what the researchers found about the chances of getting breast cancer before age 55:
- 3.6% for women who used E-HT
- 4.5% for women who used EP-HT
- The approximate percentage is 4.1% of women, who actually never used any hormone therapy
Dr. Dale Sandler, another scientist at NIEHS, said, “These results show that the decision to use hormone therapy especially EP-HT should be carefully thought through. It is necessary to know about both the benefits and the risks. This is a basic responsibility for Women and their doctors”.
Reason of Study
Previous research mostly looked at older, postmenopausal women. This new study shows that younger women may also face similar risks when using hormone therapy. The results can help doctors offer more personalized care and make better treatment plans based on each woman’s health situation.
NIH and NIEHS
Full form of NIH is The National Institutes of Health. It’s basically the main government organization. It’s worked for medical research. Which is in the United States. One part of it, called the National Institute of Environmental Health Sciences (NIEHS), studies how the environment affects people’s health and includes 27 research centers. It works to find better ways to treat and prevent diseases.
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(Reference: O’Brien, K., et al. “Use of hormone therapy and breast cancer that starts at a young age,” – Lancet Oncology, 2025”.)
