Washington ? A compound that works like estrogen, but with none of the side effects, has been found to prevent brittle bone disease in mice. The discovery may offer an alternative for older women who stopped hormone replacement therapy because of the risks of cancer and heart disease.

In a study appearing today in the journal Science, researchers say experiments with the compound, called estren, increased bone density and strength in mice that had been surgically altered to mimic menopause. The scientists said they found none of the dangerous side effects linked to estrogen.

“This seems to be superior to estrogen in its effect on the bone, but it has no effect on the sex organs,” said Dr. Stavros C. Manolagas, a researcher at the University of Arkansas for Medical Sciences and the Central Arkansas Veterans Health Care System, and the senior author of the study.

Experts on osteoporosis, the brittle bone disease, said if estren was found to work as well in humans it could substitute for the hormone replacement therapy, or HRT, that has been used to maintain bone health in women after menopause.

An estimated 20 million American women regularly were taking hormone supplements to treat post-menopausal symptoms like hot flashes and the thinning of the bones. But in July, federal scientists abruptly ended a study of the combination of estrogen and progestin after finding evidence that long-term use increased the risk of breast cancer, strokes and heart attacks. Sales of various formulations of HRT have dropped 15 percent to 40 percent since then.

At Thursday’s conclusion of a two-day meeting at the National Institutes of Health, officials urged that women not use HRT on a long-term basis.

Federal health officials estimate that 10 million people have been diagnosed with osteoporosis and another 34 million are at high risk of the disorder. Eighty percent of osteoporosis patients are women.