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FDA-approved
Bones & muscles
Teriparatide
Also called PTH(1-34)
Teriparatide (Forteo) is an FDA-approved parathyroid hormone fragment that builds new bone in people at high fracture risk from osteoporosis.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Teriparatide (sold as Forteo) is a fragment of parathyroid hormone used to build bone in people at high risk of fracture from osteoporosis. Given as a once-daily injection, it is one of the few drugs that actively stimulates new bone formation rather than just slowing bone loss. It has been FDA-approved in the U.S. since 2002, and a boxed warning about a rat bone-cancer signal was removed by the FDA in 2020.
What is teriparatide?
Teriparatide, sold under the brand Forteo (and as Bonsity), is a recombinant version of the first 34 amino acids of human parathyroid hormone, the active portion of the hormone that regulates calcium and bone. Unlike most osteoporosis drugs, which slow the breakdown of bone, teriparatide stimulates the body to lay down new bone. It was developed under the code LY333334 and approved in the United States in 2002.
How does teriparatide work?
Teriparatide binds the PTH-1 receptor on bone-building cells (osteoblasts). The effect of parathyroid hormone on bone depends on how it is delivered: continuously high levels break bone down, but a brief once-daily pulse, which is how teriparatide is given, tips the balance toward bone formation. Each daily injection stimulates osteoblasts more than it stimulates the cells that resorb bone, so bone mineral density and bone strength increase over months of treatment.
That anabolic effect translates into fewer fractures. In the Fracture Prevention Trial in postmenopausal women with prior spine fractures, teriparatide cut the risk of new vertebral fractures1 by about 65 percent compared with placebo. Because the benefit accrues with daily dosing and treatment is generally limited to a couple of years, it is often followed by an antiresorptive drug to maintain the gains.
Is it FDA-approved?
Yes. Teriparatide's FDA label has changed since approval:
| Year | Label status |
| 2002 | Approved2 for osteoporosis, with a boxed warning because high, lifelong doses caused osteosarcoma (a bone cancer) in rats, along with a 2-year limit on cumulative use |
| 2020 | After years of human data showed no increased osteosarcoma signal, the FDA removed the boxed warning and kept osteosarcoma as a standard warning |
| Now | Use beyond 2 years should be considered only if a person remains at high risk of fracture |
What is teriparatide prescribed for?
Teriparatide is prescribed for osteoporosis at high risk of fracture, including in:
- Postmenopausal women
- Men with primary or hypogonadal osteoporosis
- People with glucocorticoid-induced osteoporosis
It is generally used for those at high fracture risk rather than as a first-line drug for mild disease.
What are the side effects?
According to the prescribing information, common side effects include:
- Joint pain
- Pain
- Nausea
- Dizziness and leg cramps
- Transient drop in blood pressure on standing after a dose
More serious considerations include:
- Short-lived increases in blood and urine calcium
- Calcium deposits in the skin, including calciphylaxis
- A historical, now-downgraded concern about osteosarcoma based on rat studies
Teriparatide is avoided in people at increased baseline risk of osteosarcoma, such as those with Paget's disease or prior skeletal radiation.
Sources: FDA prescribing information for Forteo and FDA 2020 label update; the Fracture Prevention Trial (Neer et al., The New England Journal of Medicine, 2001, DOI: 10.1056/NEJM2001051034419041), indexed on PubMed. This document is educational and does not constitute medical advice.