Estrogen loss induces lung disease in mice.

Estrogen is a multitalented hormone. It plays a dominant role in the reproductive systems of women, but it's also instrumental in building strong bones. Now, research suggests that estrogen keeps the lungs working smoothly.

At the late-April Experimental Biology 2004 meeting in Washington, D.C., researchers reported that female mice deprived of estrogen by having their ovaries removed lost 45 percent of their working alveoli, the tiny sacs in the lungs that deliver oxygen to the bloodstream and remove carbon dioxide from it.

When given estrogen, the animals recovered full lung function, says Donald J. Massaro, a pulmonologist at Georgetown University School of Medicine in Washington, D.C., who presented the findings.

Earlier research had indicated that women are more susceptible to some lung diseases than men are. For example, among people over age 70 who have never smoked, women make up 85 percent of those with chronic obstructive pulmonary disease. "We wonder if it has to do with the decline in estrogen" in older women, Massaro says.

Investigating further, he and his colleagues found that two related proteins on lung-cell surfaces play distinct roles in breathing. Estrogen activates both proteins. One protein helps build new alveoli; the other stimulates alveoli to expel carbon dioxide, Massaro says. Loss of estrogen hampered both functions in mice, he says.