Calcium and exercise can only do so much. Andrea, 46, a lawyer in San Francisco who asked that her last name not be used, had a heel scan at a health fair, which indicated she was in the danger zone. When a DXA scan confirmed she was osteopenic, her doctor prescribed Fosamax, which prevents the tiny cracks caused by the osteoclasts. The drug, along with a similar drug, Actonel, has been approved to treat osteopenia—but because the osteoclasts don't get truly destructive until after menopause, the approval is only for postmenopausal women. If a woman simply has delicate bones, there's no evidence either drug will help. "I'd rather err on the side of prevention," says Andrea, who hasn't hit menopause yet. She knows several other women in their 40s whose doctors put them on the drug as well.

"That's my worst fear," says the NORA study's Siris. "A woman in her 30s or 40s finds out she has low bone density and her doctor puts her on expensive drugs she doesn't need. It's incorrect for a healthy premenopausal woman to be on Fosamax." Evista, a third drug approved to treat osteopenia in postmenopausal women, is a Selective Estrogen Receptor Modulator, or SERM, which acts like estrogen in some parts of the body but not others. Though Evista is known to slow bone loss in postmenopausal women, it has never been studied for this purpose in younger women. And last November, the first drug that actually stimulates bone growth, Forteo, was approved by the FDA, but again only for women who've been through menopause (it involves a daily injection). None of these drugs has been studied for long-term safety.

Medication is an option for postmenopausal women with osteopenia, although even then, there's no need to rush into it. No one goes from osteopenia to osteoporosis in a year. "If your bone density is low, you might decide you want to get on one of those drugs, and that's a reasonable choice. Or you might wait and get retested in a year," says Siris. The good news is that the osteoporosis drugs have dramatically helped women who already have the disease, reducing their fracture risk by as much as half.


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