All of the patients took a pill and got a shot every day for 18 months.
Half of the patients got Fosamax and a shot containing no medicine. The other half of the group got an empty pill and a shot of Forteo.
Participants got bone density scans of their hip and lumbar spine periodically throughout the study.
After 18 months of treatment, patients in the Forteo group had a 7% increase in their lumbar spine bone mineral density and a 3.8% increase in their total hip bone mineral density.
People taking Fosamax showed smaller gains, with a 3.4% increase in lumbar spine bone mineral density and a 2.4% increase in their total hip bone mineral density.
Of the 11 people who suffered a spine fracture during the study, 10 were taking Fosamax and one was taking Forteo.
The researchers -- who included Kenneth Saag, MD, of the University of Alabama at Birmingham -- report similar safety profiles for each drug.
But a journal editorial notes that the study is due to continue for another 18 months, and those results aren't in yet.
Editorialist Philip Sambrook, MD, of Australia's University of Sydney also notes that the study only included "the group most severely affected by [steroid]-induced bone loss and the most difficult to treat."
The study, published in tomorrow's edition of The New England Journal of Medicine, was funded by Eli Lilly, which makes Forteo.
In the journal, Saag reports financial ties to Eli Lilly and to Merck, which makes Fosamax. Sambrook notes no potential conflicts of interest.
Merck spokeswoman Kim Hamilton tells WebMD that Merck doesn't have an immediate comment but looks forward to reviewing the study.