What is hormone replacement therapy (HRT)?
Menopause is the time of your last period, a natural part of a woman’s aging process when menstruation stops permanently because the ovaries no longer produce the female hormones estrogen and progesterone. This usually happens between the ages of 45 and 55, coinciding with an increase in the risk of heart disease and stroke in women. It was therefore thought that replacing a woman’s natural hormones through hormone replacement therapy (HRT) might be able to prevent heart disease in older women.
However, results have so far been discouraging. Studies have shown that replacement estrogen doesn’t have the same benefits as your body’s natural estrogen, and HRT may actually slightly raise the chances of developing coronary artery disease and stroke. However, HRT is relatively safe if used for a short time to control menopausal symptoms.
There is no evidence that HRT can prevent or delay the onset of heart failure, but it has been investigated as a way to slow the decline in heart function in women with advanced heart failure.
- Overview of the Risks & Benefits of Hormone Therapy
- Hormone Therapy & Your Heart (including info on the different types of HRT)
Can HRT be used to treat heart failure?
Despite the lack of success of HRT for the prevention of coronary artery disease, a few studies have indicated that hormone replacement could be beneficial for some women with advanced heart failure. However, there is not yet enough evidence to make HRT a standard treatment these women: the only large randomized trial so far found that HRT did not improve survival. The latest treatment guidelines state that “hormonal therapies are not recommended and may be harmful” for women with heart failure. This does not mean that HRT will never be a treatment option for heart failure, only that more studies need to be done to determine if it is helpful.
The Evidence So Far
The Heart and Estrogen- Progestin Replacement Study (HERS) was a randomized trial that evaluated hormone therapy in women with coronary artery disease. One analysis of this study looked at only women who had heart failure, who made up 23% of the 2763 women in the study. HRT did not have any effect on survival over the four years of the study, 18% of the women from both the HRT and no-HRT groups survived. However, women with the most severe heart failure (NYHA class IV) were not included in the trial. In addition, coronary artery disease was the likely cause of most of the heart failure in this study, and other studies have suggested that this might be the group of women who benefit least from HRT.
A few smaller observational studies have indicated that HRT may be beneficial in some women with heart failure. In one, researchers looked at 1,134 women 50 years of age or older who had severe systolic heart failure and were enrolled in a trial of a heart failure drug. About 20% of the women were taking HRT. After 1 year, 15% of the HRT users had died compared with 27% of nonusers. After adjustment for other factors such as age, race, and severity of heart failure, women taking HRT were about 30% less likely to die than women who weren’t taking hormones. Another study of 493 women found that HRT reduced the chances of dying by about 40%, but only in women whose heart failure was not caused by coronary artery disease.
The reason for the benefits of HRT seen in these two studies are not known, but some possible explanations include:
- Improved the function of the blood vessel walls (endothelium), allowing them to relax and reducing strain on the heart
- Reduced activation of nerve and hormone signals that stress the heart muscle6
- Changes in the way the heart muscle responds to an increased workload7
For now, there is not enough evidence to determine whether HRT is beneficial or harmful when used to treat women with advanced heart failure. A large randomized trial would be required to find out if HRT should become part of the standard treatment. However, this may be difficult to accomplish because large trials of HRT to prevent heart disease and stroke (HERS and the Women’s Health Initiative Trial) have so far had disappointing results. In addition, women taking HRT have a slightly increased risk of blood clots, stroke, and breast cancer, risks that would have to be weighed against the potential benefits for women with advanced heart failure.