During the 1990s, most doctors felt strongly that hormone replacement therapy (HRT) provided many health benefits to postmenopausal women. These purported benefits were related to reduced bone loss and improvements in lipid profiles that were assumed to protect women from cardiovascular disease.
Then, beginning in the late 1990s, the results of three randomized clinical trials stunned women and their doctors with news that, not only did HRT therapy fail to provide many of the health benefits attributed to it, but women taking HRT were more likely to have cardiovascular disease than women not taking it. The medical dogma rapidly changed, and HRT came to be regarded as a producer of cardiac risk. The use of HRT among postmenopausal women plummeted.
Beginning in 2004, investigators began taking a closer look at the data from these (and other) studies, and they noticed something different -- younger postmenopausal women taking HRT did not appear to have the same related risk as older women using HRT. Indeed, there was evidence that in these younger women, HRT may do what everyone in the 1990s thought it did -- reduce the risk of heart disease. These findings led to further study.
As a result, the American Association of Clinical Endocrinologists (AACE) released a statement in January 2008 endorsing the use of HRT (with estrogen) in younger postmenopausal women. In their statement, the AACE cited information from the Nurses' Health Study showing that women beginning therapy with HRT (with either estrogen alone or with estrogen plus progestin) soon after menopause had a significant reduction in cardiac risk. The AACE statement cited several other studies showing similar findings, though they noted that women treated with estrogen alone had a somewhat lower cardiovascular risk (though the difference was not statistically significant) than women treated with estrogen plus progesterone.
In general, it appears that HRT may be beneficial for women less than 10 years into menopause or less than 60 years of age. Among older women, however, adding HRT seems to produce more cardiovascular events during the first two years of HRT therapy. But the data suggest that even among these older women, those who are able to stay on HRT for a longer period of time may end up with a reduced cardiovascular risk.
The rub is that the new AACE statement currently endorses HRT with estrogen alone. Unfortunately, estrogen without progesterone may increase the risk of endometrial cancer - which practically limits this variety of HRT to women who have had hysterectomies.
HRT is known to increase the risk of blood clotting, at least for a few years. (Women with a history of venous thrombosis have always been cautioned about taking HRT.) So, for women who have spent enough time in menopause to have had the "opportunity" to develop coronary artery disease, suddenly starting HRT might bring about the intravascular blood clotting that causes heart attack and stroke in patients with atherosclerosis. But in younger women, who haven't had sufficient time to develop atherosclerotic plaques in their arteries, the increased propensity to clot does not produce cardiovascular "events." Taking HRT may help to prevent atherosclerotic disease from developing over the long term because of the favorable changes in lipid profile (and probably other beneficial metabolic changes.)
Beginning HRT early (before atherosclerosis develops) may have continued, long-term cardiovascular benefits; whereas beginning it later may precipitate heart attacks or strokes since atherosclerosis may already be present.
The official AACE recommendation, however, is of limited practical value to women who have not had hysterectomies, since the risk of endometrial cancer is increased with estrogen-only therapy. This, despite the fact that the data actually cited by AACE in formulating their recommendation seems to offer nearly equivalent support for the use of estrogen plus progesterone in these younger women. It seems likely that official medical organizations like AACE are moving particularly cautiously -- especially in light of the whipsaw changes in HRT recommendations we have already seen in recent years.
The bottom line is that women who are in their early menopausal years and who would like to consider HRT should should engage their doctors in a long talk. Using HRT with estrogen plus progesterone in younger post-menopausal women is still not within the purview of official recommendations - but it's a lot closer than it was previously, and the data supporting it looks remarkably similar to the data supporting estrogen alone.
Press Release: American Association of Clinical Endocrinologists. "AACE Analysis shows no excess cardiovascular risk from hormone replacement therapy for most patients." January 2, 2008.
"Position Statement on Hormone Replacement Therapy (HRT) and Cardiovascular Risk," American Association of Clinical Endocrinologists.