Opposite bone remodeling effects of teriparatide and alendronate in increasing bone mass

Antiresorptive agents for the treatment of osteoporosis suppress bone remodeling and reestablish bone turnover at a lower rate to reduce bone loss. Recombinant teriparatide (human parathyroid hormone 1-34) stimulates bone formation, increases bone mass, and improves bone microarchitecture. We contrasted the effects of once-daily doses of 20 mug of teriparatide and 10 mg of alendronate sodium on bone mineral density (BMD) and markers of bone turnover.

Markers of bone turnover and areal BMD were assessed in 203 postmenopausal women with osteoporosis in an 18-month randomized parallel double-blind study; volumetric BMD was measured in a subset of women.

Teriparatide significantly increased markers of bone turnover that peaked at 6 months (serum procollagen type I N-terminal propeptide, 218%, and urinary N-telopeptide corrected for creatinine, 58%; P<.001); alendronate significantly decreased the markers at 6 months (-67% and -72%, respectively; P<.001). At 18 months, areal and volumetric spine BMDs were significantly higher with teriparatide than with alendronate (10.3% vs 5.5% [P<.001] and 19.0% vs 3.8% [P<.01], respectively). Areal femoral neck BMD was significantly higher than baseline in the teriparatide and alendronate groups (3.9% and 3.5%, respectively). There were no significant differences in trabecular femoral neck BMD between the teriparatide and alendronate groups (4.9% and 2.2%, respectively). Cortical volumetric femoral neck BMD was significantly different between the teriparatide and alendronate groups (-1.2% and 7.7%, respectively; P = .05).

Two distinct options for the management of osteoporosis lead to increases in BMD by opposite mechanisms of action on bone remodeling.