Another Piece of the Hormone and Heart Disease Puzzle
April 11, 2000 (Lake Tahoe, Calif.) -- The decision of whether to take hormone replacement therapy remains a riddle for women, particularly those concerned about heart disease.
Researchers hope to offer another clue in a report released in this week's issue of the Journal of the American Medical Association. They found that a substance in the blood stream called lipoprotein(a) appears to be the most significant cholesterol-related risk factor for a second heart attack. This lipoprotein -- also called Lp(a) -- is affected by estrogen in postmenopausal women, but the result of hormone therapy in women who don't have abnormally high Lp(a) may not be beneficial.
The study set out to see the effect of hormone replacement therapy, using estrogen and progestin, on the rate of new heart attacks in almost 2,800 postmenopausal women with heart disease over four years.
"In [the study], there was an increase in the rate of heart attacks in the first year and later a decrease. But overall, for four years the rate of heart attack was identical in the hormone-treated group and the placebo group," lead investigator Stephen B. Hulley, MD, MPH, tells WebMD. "We wondered whether Lp(a) might offer a clue to that."
According to Hulley, Lp(a) tends to increase blood clotting. Even though Lp(a) resembles LDL, or "bad" cholesterol, drugs commonly used to lower unusually high bad cholesterol levels have no effect on Lp(a).
The researchers found that the estrogen and progestin therapy had a more favorable effect than placebo on women with high levels of Lp(a) but a more adverse effect in women with low levels of Lp(a). In fact, those women had a slightly higher risk of heart attack than the placebo group.
Michael Criqui, MD, tells WebMD, "This might influence [which women] have a higher potential for benefit from estrogen and women that don't have as much potential for benefit, but we can't say that yet." Criqui is a professor of family medicine and prevention at the University of California, San Diego, and was not involved in the study.