The Landmark Trial That Proved Parathyroid Hormone Peptide Prevents Fractures in Osteoporosis

Randomized, placebo-controlled trial of 1,637 postmenopausal women with prior vertebral fractures across multiple countries. Women self-administered daily subcutaneous injections of PTH(1-34) at 20 μg, 40 μg, or placebo. Vertebral radiographs were taken at baseline and study end (median 21 months). Bone mineral density was measured serially by DXA scan. The primary outcome was new vertebral fractures.

This is one of the most important trials in osteoporosis history. Before this study, all osteoporosis drugs worked by slowing bone breakdown — parathyroid hormone was the first treatment proven to actually build new bone (an anabolic approach). This trial directly led to the FDA approval of teriparatide (Forteo) in 2002, which became the first bone-building peptide drug and changed how severe osteoporosis is treated.

This trial launched the era of anabolic bone therapies and proved that a peptide hormone fragment could do what no previous drug had done: build new bone rather than just prevent its loss. Teriparatide became the standard of care for severe osteoporosis and paved the way for newer anabolic agents like abaloparatide (a PTHrP analog) and romosozumab. The concept that intermittent low-dose parathyroid hormone stimulates bone formation — even though continuous high levels destroy bone — remains one of the most elegant pharmacological paradoxes in medicine.

The trial was stopped early (median 21 months instead of the planned longer duration) due to a concurrent finding that rats given high-dose PTH developed bone tumors (osteosarcoma) — though this has never been observed in humans. The 40 μg dose caused bone loss at the radial shaft, suggesting cortical bone responds differently. Long-term effects beyond 21 months and the question of what happens when treatment stops weren't addressed in this trial.