Teriparatide: The Only Drug That Builds New Bone
Teriparatide is a synthetic parathyroid hormone fragment that stimulates osteoblasts to form new bone — the only widely approved anabolic osteoporosis drug, limited to 2 years of use.
Teriparatide (brand name Forteo) is a synthetic fragment of parathyroid hormone (PTH 1-34) and the principal anabolic therapy for Osteoporosis: When Bone Breakdown Outpaces Bone Building. Unlike Bisphosphonates: The First-Line Defense Against Osteoporosis and Denosumab: The Antibody That Stops Bone-Eating Cells but Can't Be Stopped Easily, which slow bone *loss*, teriparatide stimulates Osteoblasts: The Bone-Building Cells That Strengthen Your Skeleton to build *new* bone. ## Mechanism Paradoxically, continuous high PTH causes bone loss (as in hyperparathyroidism), but intermittent low-dose PTH — a daily subcutaneous injection — preferentially stimulates osteoblast activity over osteoclast activity, producing net bone formation. The drug increases both bone mineral density and bone quality (trabecular microarchitecture). ## Limitations Treatment is limited to a maximum of **2 years** due to concerns from animal studies showing osteosarcoma (bone cancer) in rats given high-dose, lifelong PTH. Human osteosarcoma risk appears negligible at therapeutic doses and durations, but the precautionary limit remains. After discontinuation, patients must transition to an anti-resorptive drug (bisphosphonate or denosumab) to maintain gains. ## Clinical Use Reserved for severe osteoporosis, patients with prior fractures, or those who have failed other therapies. Cost is significant (~$3,000/month without insurance in the US).