Osteoporosis affects nearly 8 million women over the age of 50. By 2015, this number will jump to 12 million. Those who suffer from this bone-wasting disease can take medication to slow the process, but the bone that was lost could not be replaced by drug treatment, until now.

A new medication, developed by Eli Lilly and called Forteo, is the first to offer the hope of replacing bone lost to osteoporosis, and it could be available by the end of 2001. In a recent study, Forteo stimulated bone growth in women with osteoporosis, resulting in a reduced risk of repeat backbone fractures of 65% to 69%. The risk of fracture in other parts of the body was also reduced by about 50%.

But Forteo requires daily injections of human parathyroid hormone (PTH) produced by genetically engineered bacteria. It's inconvenience will make it impractical for prevention of osteoporosis until a pill or inhaler is developed.

As for the drug's tolerability, the most common side effects were nausea (18%), headache (13%), dizziness (6%), and leg cramps (3%).