The different effects of oral vs. transdermal hormone replacement therapy (HRT) on heart disease risk factors make a woman's choice between taking estrogen via pill or patch more than a convenience issue, says a Penn State researcher. Dr. Sheila West, assistant professor of biobehavioral health, is lead author of a new study, which is one of the first to look at the effects of the estrogen pill vs. the patch on heart disease risk factors beyond blood pressure and cholesterol.
The study results showed that the HRT pill and patch had similar positive effects on the tightness or constriction of blood vessels, total cholesterol and low-density lipoprotein cholesterol (LDLs, the "bad" cholesterol). However, the research team found different effects on high density lipoprotein (HDLs, the "good" cholesterol) and triglycerides depending on whether the woman was taking HRT pills or using a patch to deliver estrogen.
In addition, the study found that women who used either the estrogen pill or the patch had lower blood pressure during psychological stress. West says this blood pressure lowering effect might be a new way to explain how estrogen protects women from heart disease.
"Women may have special reasons for wanting to choose the patch or the estrogen pill," says the Penn State researcher. "If, for example, a woman has low HDLs, she might choose oral HRT since subjects in our study and other studies showed no change in the beneficial HDLs while on transdermal therapy. "On the other hand, a woman might want to select the patch if her triglycerides were already high, since oral therapy increases this factor which is associated with a higher risk of heart disease." The study is detailed in the April issue of the American Journal of Obstetrics and Gynecology in a paper, "Transdermal Estrogen Reduces Vascular Resistance and Serum Cholesterol in Postmenopausal Women." West conducted the study as part of her dissertation when she was a doctoral student at the University of North Carolina at Chapel Hill. Her co-authors are University of North Carolina, Chapel Hill, faculty members Dr. Alan L. Hinderliter, associate professor of medicine; Dr. Ellen C. Wells, associate professor of medicine; Dr. Susan S. Girdler, assistant professor of psychiatry; and Dr. Kathleen C. Light, professor of psychiatry.
In their paper, the researchers write, "Trials to examine whether HRT reduces risk of morbidity and mortality in women without preexisting coronary disease are not yet available. Furthermore, the relatively recent introduction of the estrogen patch means that its long-term impact on the risk of coronary events in postmenopausal women is also unknown. Until the appropriate longitudinal studies can be completed, randomized clinical trials examining multiple markers of coronary risk are critical to establish the efficacy of novel hormone preparations."
The primary goal of the researchers' study was to compare changes in multiple cardiac risk factors in healthy women receiving HRT via either the pill or the patch. The researchers compared 10 postmenopausal women receiving HRT via the Estraderm patch with 23 women taking an estrogen pill, Premarin, for six months. Nine subjects received placebos. The women who used the estrogen patch also took progesterone via pill, Cycrin. The estrogen pill takers also received progesterone. The subjects were tested for cardiovascular responses during rest and under stress before they began taking the medication and again after three and six months of treatment. The researchers looked at the subjects' responses both during rest and under stress because there have been recent reports that HRT decreases cardiovascular reactivity to psychological stress.
The stressors included describing a recent life experience which caused stress or anger, two challenging cognitive tests, and a physical stressor in which a bag of ice and cold water was held on the forehead for four minutes.
The team's results confirmed earlier studies which showed that both HRT pill and patch therapy lowers blood pressure during psychological stress.
In addition, the study was the first to show that the ability of the blood vessels to relax increases with both estrogen pills and patches and that this relaxation response persists even when the subjects were under stress.
"The study shows that the patch and the pill equally impact the risk factors studied, except for HDLs and triglycerides," West notes. "The estrogen pill seems to elevate the triglycerides while the patch does less so. Oral estrogen also increases HDLs while the transdermal patch does not. "It remains to be seen, perhaps in a larger study, whether the effect on HDLs means women are not equally protected by the patch and the pill," she says.
