New Findings on Hormone Replacement Therapy

Estrogen-only therapy benefits some women in their 50s

/ Author:  / Reviewed by: Joseph V. Madia, MD

You may remember some years ago when a large women's study was stopped because one of the therapies being tested was shown to actually increase the risk of breast cancer, heart attacks and strokes.

The statistics from the Women's Health Initiative were scary. As a result of these findings, the use of all forms of hormone replacement therapies for treating symptoms of menopause has decreased dramatically in the United States and around the world.

New study shows estrogen benefits certain women

A new study from the same researchers finds that a particular kind of hormone therapy - estrogen only - can actually benefit some women - those in their 50s who have had a hysterectomy and therefore have no uterus.

Six years after using estrogen-only therapy, middle-aged women who've had hysterectomies, saw a significantly lower risk of developing breast cancer, having a heart attack and other chronic diseases.

These new findings do not dispute all of the earlier findings showing that using the combination of estrogen and progestin is still problematic.

Let's try to sort out this data that's decidedly confusing.


The Women's Health Initiative (WHI) was funded by the National Institutes of Health and began in 1991 to look at health issues facing postmenopausal women. Three diseases were of particular interest - heart disease, cancer and osteoporosis.

The study was divided into four components examining the risks and benefits of taking:

  • Estrogen + progestin vs. placebo (sugar pill)
  • Estrogen only vs. placebo (This group was made up of women who had past hysterectomies.)
  • Calcium and Vitamin D
  • No therapy

Trial stopped because estrogen + progestin therapy found to be unsafe

The trial was stopped abruptly early in 2002 when researchers found that compared with the placebo, estrogen plus progestin therapies increased risks of:

  • Heart attacks
  • Strokes
  • Blood clots
  • Breast cancer

It's important to note that risks from taking the combination of estrogen and progestin still exist.

Latest findings relate only to women in their 50s who have had hysterectomies

The first and most important thing to know about the new findings is that they pertain only to certain women:

  • Women have had hysterectomies and had their uterus surgically removed
  • Postmenopausal women in their 50s

Roughly one-third of women in their 50s have had hysterectomies, so this group numbers in the millions.

Women followed for 11 years

A total of 10,739 women with no uterus were a part of the original trial. Even though they stopped taking estrogen in 2004, researchers continued to follow them and learned some interesting and important information as a result.

Estrogen-only therapy cuts breast cancer risk

Women in their 50s who have had hysterectomies benefit from estrogen-only therapy. Women who have a uterus can't take estrogen alone because of the risk of uterine cancer.

Here's what the study, published in The Journal of American Medical Association.

For women who took estrogen for about six years and stopped, researchers found:

  • 23 percent decreased risk of breast cancer
  • Lower risk of strokes and blood clots in legs and lung

While women in their 50s are taking estrogen only, they benefit from:

  • Lower incidences of heart attacks, colorectal cancer, death and overall chronic diseases

Estrogen not safe for women in their 70s

This study also showed that estrogen-only therapy is not appropriate for women in their 70s, however. Older women taking estrogen had increased risks of breast cancer, heart disease, colorectal cancer, chronic diseases and death.

Summarizing the findings

Dr. Andrea LaCroix, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle and the study's lead author, summarized the study during a PBS interview, "It suggests, in the 50s, that women can be very reassured that, if they decide to take hormone therapy for relief of menopause symptoms or for other reasons, that they're not going to have an increased risk of breast cancer; they're not going to have more heart attacks. In fact, their risks of those outcomes might be lower. They’re not going to have more deaths. Their risk of death might be lower. And it suggests, for women in their 70s, that starting estrogen has some serious consequences in terms of increasing their

Dr. LaCroix goes on to say, "And for women with a uterus, I think they need to pay attention to that whole other trial on estrogen plus progestin."

Concerns remain

The type of estrogen used in the study is known as conjugated equine estrogen (CEE) which comes from pregnant mares. Premarin is the most common brand name of CEE. Some scientists have said more research is needed to learn if the study's findings hold up when other forms of estrogen, including treatments containing estridiol, are used.

Dr. LaCroix suggests that further study is needed to learn exactly how estrogen impacts breast cancer.

Reviewed by: 
Review Date: 
April 7, 2011
Last Updated:
April 8, 2011