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That group would include 30 percent to 50 percent of those with drug-caused osteoporosis, he said. The U.S. Food and Drug Administration already has approved use of teriparatide for the condition.

The anabolic steroid is a better treatment, because bisphosphonates do not actually promote bone growth, added Dr. Robert R. Recker, professor of medicine at Creighton University and a member of the Osteoporosis Research Center there. Rather, they prevent bone destruction by natural processes such as apoptosis (natural cell death), he said

"There is a greater need for a bone-forming agent, one that interferes with the apoptosis of bone cells," Recker said. "The condition is not so much a low bone mass disease but a disease of bone cells that results in too much remodeling. Bisphosphonates lower remodeling. [Teriparatide] increases new bone formation."

But longer-term studies are still needed to assess teriparatide's effects over prolonged periods, Recker said.

"Not one study has gone long enough to see if you get more benefits by using it for a long time," he said. "It may be good for 24 months. That remains to be seen."

More information

There's more on medication-linked bone loss at the American College of Rheumatology.

SOURCES: Kenneth G. Saag, professor, medicine and epidemiology, University of Alabama at Birmingham; Robert R. Recker, M.D., professor, medicine, Creighton University, Omaha, Neb.; Nov. 15, 2007, New England Journal of Medicine