Teriparatide
The first 34 amino acids of parathyroid hormone, injected daily to build bone in osteoporosis
Teriparatide is the active fragment of parathyroid hormone, the first 34 of its 84 amino acids, injected under the skin once a day. Approved as Forteo for osteoporosis at high risk of fracture, it cut new spine fractures by about two thirds against placebo in its first trial and by more than half against risedronate in a 1,360-woman head-to-head. In pulses it builds bone; given continuously the same hormone removes it.
What is it?
Parathyroid hormone raises blood calcium, and when it is high all the time it strips bone. Given as a brief daily pulse it does the opposite: bone formation outruns resorption. Teriparatide is that pulse, the first 34 amino acids of the hormone, injected once a day. Its label says it peaks about 30 minutes after a 20 microgram dose and falls to unmeasurable levels within three hours, with a half-life of about an hour.
The first fracture trial, published in 2001, randomised 1,637 postmenopausal women who already had a spine fracture to 20 or 40 micrograms a day or placebo. Over a median of 21 months, new spine fractures occurred in 14% on placebo against 5% and 4% on the two doses, relative risks of 0.35 and 0.31, and new non-spine fragility fractures fell from 6% to 3%. Spine bone density rose by 9 and 13 percentage points more than placebo. The higher dose built more bone but prevented no more fractures and caused more side effects, which is why 20 micrograms became the dose.
The VERO trial asked the harder question: is it better than a standard drug? 1,360 postmenopausal women with severe osteoporosis took 20 micrograms of teriparatide daily or 35 mg of risedronate weekly for two years, each with a matching dummy. New spine fractures occurred in 5.4% on teriparatide against 12.0% on risedronate, and clinical fractures in 4.8% against 9.8%; non-spine fragility fractures were fewer (4.0% against 6.1%) but not significantly so.
In people on long-term steroids, whose bones thin for a different reason, an 18-month trial in 428 women and men compared it with alendronate. Spine bone density rose 7.2% on teriparatide against 3.4% on alendronate, and new spine fractures occurred in 0.6% against 6.1%; non-spine fractures did not differ. More patients on teriparatide had a high calcium reading.
Combining it with denosumab, another osteoporosis drug, raised bone density more than either alone: in the 94-woman DATA trial the combination raised spine density 9.1% in a year, against 6.2% for teriparatide alone and 5.5% for denosumab, with larger hip gains as well (total hip 4.9% against 0.7% and 2.5%). The trial was not large enough to measure fractures.
It is less convincing outside osteoporosis. In 40 women with a broken upper arm and 35 very elderly patients with pelvic fractures, it did not speed healing on imaging. In 349 adults with osteogenesis imperfecta, the brittle-bone disease, two years of teriparatide followed by zoledronic acid raised bone density but did not reduce fractures (36.9% against 36.4% on standard care).
Its main safety story was a rat finding. Rats given high doses for most of their lives developed osteosarcoma, a bone cancer, so Forteo was approved with a boxed warning and a two-year lifetime limit. A 15-year US surveillance study then found three teriparatide users among 1,173 interviewed osteosarcoma patients, against 4.17 expected, and the label was updated in 2020: the boxed warning was removed and the two-year limit revised. Today's label still tells prescribers to avoid it in people at higher risk of osteosarcoma and allows use beyond two years only if fracture risk remains high.
Mechanism of Action
Teriparatide activates the PTH1 receptor on bone-forming cells. Given as a short daily pulse it builds more bone than it removes; held high continuously, the same signal removes bone.
PTH1 receptor on osteoblasts
It binds the type 1 parathyroid hormone receptor, a G-protein-coupled receptor on osteoblasts and osteocytes, the cells that lay down and sense bone.
Pulse, not plateau
A daily injection peaks in about 30 minutes and clears within about three hours (label). This intermittent signal favours formation; continuous exposure, as in hyperparathyroidism, favours resorption.
Bone gain on scans
In the first trial, spine density rose 9 percentage points more than placebo at 20 µg and 13 at 40 µg, and femoral-neck density 3 and 6 points more.
Calcium effects
It transiently raises blood calcium, the reason for the label's warnings about high calcium, kidney stones and digoxin.
Published Research
The studies behind teriparatide, read from their PubMed abstracts: the trials that established it, the head-to-heads, a combination, safety surveillance, and the trials where it did not help.
The first fracture trial: 1,637 women
Postmenopausal women with a prior spine fracture took 20 or 40 µg daily or placebo for a median of 21 months. New spine fractures occurred in 14% on placebo against 5% and 4% (relative risks 0.35 and 0.31); non-spine fragility fractures fell from 6% to 3%. Side effects were minor (occasional nausea and headache).
Steroid-induced osteoporosis: against alendronate, 428 patients
Women and men on long-term glucocorticoids took 20 µg teriparatide or 10 mg alendronate daily for 18 months. Spine bone density rose 7.2% against 3.4%; new spine fractures occurred in 0.6% against 6.1%, and non-spine fractures did not differ (5.6% against 3.7%). More teriparatide patients had a raised calcium reading.
DATA: with denosumab, 94 women
Postmenopausal women took 20 µg teriparatide daily, 60 mg denosumab every six months, or both. At 12 months spine density rose 9.1% on the combination against 6.2% and 5.5%, and total-hip density 4.9% against 0.7% and 2.5%. Fractures were not measured.
Osteosarcoma surveillance: 15 years in the US
Of 1,173 osteosarcoma patients interviewed (2003-2016), three had used teriparatide before diagnosis, against 4.17 expected from background rates: a standardised incidence ratio of 0.72 (90% CI 0.20 to 1.86), no different from the background incidence.
VERO: teriparatide against risedronate, 1,360 women
Postmenopausal women with severe osteoporosis took 20 µg of teriparatide daily or 35 mg of risedronate weekly for 24 months. New spine fractures occurred in 5.4% against 12.0% (risk ratio 0.44) and clinical fractures in 4.8% against 9.8%; non-spine fragility fractures were 4.0% against 6.1%, not significant.
Osteogenesis imperfecta: 349 adults
Two years of daily teriparatide followed by zoledronic acid, against standard care. Fractures occurred in 36.9% against 36.4%, despite significantly greater gains in spine and hip bone density, which the authors read as bone quality rather than density driving fractures.
An oral PTH(1-34) tablet: 161 women
Daily tablets of 0.5 to 2.5 mg or placebo for six months. At 2.5 mg, formation markers rose about 30% within a month while resorption fell, and bone density rose by 2.7% at the spine, 1.8% at the hip and 2.8% at the femoral neck.
Pelvic fracture healing: 35 patients
20 µg daily or placebo for three months in patients averaging 82 years. Healing on CT was no better (50% against 53% healed) and pain fell equally in both groups, but physical performance improved on teriparatide and not on placebo.
Upper arm fracture: 40 women
Four weeks of 20 µg daily or control treatment after a proximal humerus fracture. There were no significant differences in pain, strong painkiller use or function, and no radiographic sign of faster healing.
Dosing Data
Teriparatide is taken as one 20 microgram injection under the skin each day, into the thigh or abdomen, from a prefilled pen.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the studies above and the label.
Contraindications & Cautions
Warnings from the Forteo prescribing information (DailyMed set aae667c5, version 44, effective August 3, 2026).
Legal Status
Teriparatide is an approved prescription drug in the US and the EU.
Frequently Asked Questions
?What is teriparatide?
The first 34 amino acids of parathyroid hormone, injected daily to build bone in osteoporosis. It is sold as Forteo in the US and Forsteo in the EU, with follow-on and biosimilar versions.
?How well does it prevent fractures?
In its first trial, new spine fractures fell from 14% on placebo to 5% on 20 micrograms a day. In VERO they occurred in 5.4% on teriparatide against 12.0% on risedronate over two years.
?Why is it given as a daily injection rather than continuously?
Because the effect depends on the pattern. A short daily pulse favours bone formation; a constant high level of parathyroid hormone, as in hyperparathyroidism, removes bone. The label says it is gone from the blood within about three hours.
?Does it cause bone cancer?
High doses caused osteosarcoma in rats, so it was approved with a boxed warning. A 15-year US surveillance study found no more cases than expected (three against 4.17), and the boxed warning was removed in 2020. The label still says to avoid it in people at higher osteosarcoma risk.
?How long can it be used?
The label says use for more than two years in a lifetime should be considered only if fracture risk remains or becomes high again.
?Does it help a broken bone heal faster?
No clear benefit: neither an upper-arm nor a pelvic fracture trial found faster healing, although physical performance improved in the pelvic trial.
?Can it be combined with other osteoporosis drugs?
Denosumab added to it raised bone density more than either alone in the 94-woman DATA trial, but no combination trial cited here measured fractures.
?Is there a tablet?
An oral PTH(1-34) tablet raised bone density in a 161-woman, six-month trial; it is not approved.
References
- [fda] FDA. Drugs@FDA (openFDA): FORTEO (teriparatide) injection and follow-on teriparatide products, prescription. Read September 30, 2026.
- [fda-pi] Forteo (teriparatide) injection Prescribing Information, sections 1 and 2 (DailyMed version 44, effective August 3, 2026; read September 30, 2026).
- [pubmed] Neer RM, et al. "Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis." N Engl J Med, 2001;344(19):1434-41. PMID: 11346808.
- [pubmed] Saag KG, et al. "Teriparatide or alendronate in glucocorticoid-induced osteoporosis." N Engl J Med, 2007;357(20):2028-39. PMID: 18003959.
- [pubmed] Tsai JN, et al. "Teriparatide and denosumab, alone or combined, in women with postmenopausal osteoporosis: the DATA study randomised trial." Lancet, 2013;382(9886):50-6. PMID: 23683600.
- [pubmed] Gilsenan A, et al. "Teriparatide Did Not Increase Adult Osteosarcoma Incidence in a 15-Year US Postmarketing Surveillance Study." J Bone Miner Res, 2021;36(2):244-251. PMID: 32990990.
- [pubmed] Kendler DL, et al. "Effects of teriparatide and risedronate on new fractures in post-menopausal women with severe osteoporosis (VERO): a multicentre, double-blind, double-dummy, randomised controlled trial." Lancet, 2018;391(10117):230-240. PMID: 29129436.
- [pubmed] Hald JD, et al. "Teriparatide Plus Zoledronic Acid for Osteogenesis Imperfecta: A Randomized Clinical Trial." JAMA, 2026;336(2):116-124. PMID: 42133304.
- [pubmed] Tripto-Shkolnik L, et al. "Oral daily PTH(1-34) tablets (EB613) in postmenopausal women with low BMD or osteoporosis: a randomized, placebo-controlled, 6-month, phase 2 study." J Bone Miner Res, 2024;39(6):672-682. PMID: 38578978.
- [pubmed] Nieves JW, et al. "Teriparatide and pelvic fracture healing: a phase 2 randomized controlled trial." Osteoporos Int, 2022;33(1):239-250. PMID: 34383100.
- [pubmed] Johansson T. "PTH 1-34 (teriparatide) may not improve healing in proximal humerus fractures. A randomized, controlled study of 40 patients." Acta Orthop, 2016;87(1):79-82. PMID: 26179771.
- [pubmed] Krege JH, et al. "Teriparatide and Osteosarcoma Risk: History, Science, Elimination of Boxed Warning, and Other Label Updates." JBMR Plus, 2022;6(9):e10665. PMID: 36111201.
- [pubmed] Miller PD, et al. "Effect of Abaloparatide vs Placebo on New Vertebral Fractures in Postmenopausal Women With Osteoporosis: A Randomized Clinical Trial." JAMA, 2016;316(7):722-33. PMID: 27533157.
- [other] EMA medicines dataset: Forsteo (teriparatide), authorised June 10, 2003; biosimilars include Terrosa, Movymia and Livogiva. Read October 5, 2026.
Sources & Citations
Studies were read from their PubMed records (October 5, 2026); the label, Drugs@FDA and the EMA database are listed below with their read dates.
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