Using data from two randomized, double-blind, placebo-controlled trials from the Women's Health Initiative, UI researchers and their colleagues studied more than 22,500 women, ages 50 to 79, from 40 clinical centers across the United States, including the UI. Women who had a hysterectomy (nearly 8,400 women) received either estrogen or placebo; women who had not had a hysterectomy (around 14,200 women) received estrogen plus progestin.

The researchers found that both trials showed a greater risk of gallbladder disease or gallstone surgery with estrogen therapy. Women taking estrogen had an 80 percent increased risk for inflammation of the gallbladder and an 86 percent greater risk for gallstones. Women taking estrogen plus progestin had a 54 percent increased risk for inflammation and 68 percent greater risk for gallstones. Gallstones in the gallbladder affect between 10 to 15 percent of the U.S. population, the study authors noted.

Among women who had a hysterectomy, estrogen-alone therapy contributed to 31 excess events per 10,000 women annually. In the estrogen plus progestin trial, there were 20 excess events per 10,000 women annually.

"This is an important finding that is consistent with earlier studies that were not randomized trials," said Robert B. Wallace, M.D., UI professor of epidemiology and internal medicine and one of the study authors. "It is one more part of the equation that women must consider when deciding about the use of estrogen therapy after menopause." Wallace is the Irene Ensminger Stecher Professor of Cancer Research at the UI.

Dominic Cirillo, a UI graduate research assistant in epidemiology, is a co-author on the published study. Other co-authors are Rebecca Rodabough, Andrea LaCroix, Ph.D., and Joseph Larson at the Fred Hutchinson Cancer Research Center in Seattle, Wash; Philip Greenland, M.D., at the Feinberg School of Medicine at Northwestern University; and Marian Limacher, M.D., at the University of Florida College of Medicine.

The study was funded by the National Heart, Lung and Blood Institute.

For more information:

Robert B. Wallace, M.D.

National Heart, Lung and Blood Institute