Side by side

1. 1.Intermittent daily exposure to PTH stimulates osteoblasts, the cells that build bone, more than it stimulates osteoclasts, the cells that break it down.
2. 2.The result is new bone formation on trabecular and cortical surfaces, with gains in bone mineral density and improvements in bone architecture.
3. 3.Continuous PTH exposure has the opposite net effect — bone resorption. Dose timing, not just the molecule, determines the result.
4. 4.This 'anabolic window' is why teriparatide is given as a short daily course, usually followed by an antiresorptive drug to lock in the gains.

• Postmenopausal osteoporosis with prior fractures (pivotal trial)
• Male osteoporosis
• Glucocorticoid-induced osteoporosis
• Severe osteoporosis where other drugs have failed
• Fracture healing (investigated, results mixed)

• About 65% reduction in vertebral fractures and 53% reduction in non-vertebral fractures over a median 19 months in the pivotal trial
• Spinal bone mineral density increases of roughly 9–13%
• Rapid early rise in bone-formation markers
• Modest, transient increases in serum calcium

• Nausea and dizziness
• Leg cramps
• Transient hypercalcaemia
• Brief drop in blood pressure after the first doses (orthostatic hypotension)
• Injection-site reactions
• Osteosarcoma observed in rats — a boxed warning; human risk after short courses is not established

Research context only — this is a prescription medicine. The pivotal trial used 20 micrograms subcutaneously once daily for a median of 19 months; regulators limit total treatment to 24 months. Calcium and vitamin D are usually co-prescribed and bone density is monitored.

Research context only