Teriparatide and abaloparatide: the peptides that build bone

How a hormone that takes calcium from bone can build it

Parathyroid hormone (PTH) raises blood calcium, partly by releasing it from bone. Given continuously, as in overactive parathyroid glands, it thins bone. Given as a brief daily pulse, it does the opposite: it stimulates the cells that lay down new bone more than the cells that remove it. It is a striking example of the same molecule doing opposite things depending on how it is delivered. That paradox, intermittent exposure tipping the balance towards formation, is the basis of both drugs, as a 2025 review by an international osteoporosis group sets out (review) ¹.

Teriparatide is the first 34 amino acids of human PTH, the part that activates the PTH receptor. Abaloparatide is a synthetic peptide based on PTH-related protein, a cousin hormone that acts on the same receptor. Both are daily injections under the skin, and both are approved for people with osteoporosis at high risk of fracture (dataset) ². Teriparatide, sold as Forteo, now also has follow-on versions listed on Drugs@FDA; abaloparatide, as Tymlos, has been approved in the US since April 2017 (dataset) ².

Teriparatide: the trial that proved it

The Fracture Prevention Trial randomised 1,637 postmenopausal women who had already had a spine fracture to daily teriparatide 20 or 40 µg, or placebo, for 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; new non-spine fragility fractures fell from 6% to 3%. Spine bone density rose 9 and 13 percentage points more than placebo, and side effects were minor, mainly occasional nausea and headache (randomised trial) ³.

The trial was stopped early, not because of anything seen in the women but because of a finding in rats, discussed below (review) ⁴.

Against a standard drug: VERO

Showing a drug beats placebo is one thing; showing it beats existing treatment is another. In VERO, 1,360 postmenopausal women with severe osteoporosis took teriparatide 20 µg daily or risedronate, a bisphosphonate, weekly for 24 months. New spine fractures occurred in 5.4% on teriparatide against 12.0% on risedronate, a risk ratio of 0.44 (randomised trial) ⁵. Clinical fractures were also fewer (4.8% against 9.8%), while the difference in non-spine fragility fractures, 4.0% against 6.1%, was not significant (randomised trial) ⁵. For people at very high fracture risk, that is a meaningful head-to-head advantage over a standard drug.

Abaloparatide: ACTIVE and after

In ACTIVE, 2,463 postmenopausal women with osteoporosis received abaloparatide 80 µg daily, placebo or open-label teriparatide for 18 months. New spine fractures and non-spine fractures were less frequent with abaloparatide than placebo, bone density rose more, and hypercalcaemia, a raised blood calcium, was less common with abaloparatide than with teriparatide (3.4% against 6.4%) (randomised trial) ⁶. The trial was not designed to show that abaloparatide prevents more fractures than teriparatide, and its authors called for more research on that comparison.

Anabolic drugs are usually followed by a drug that preserves the new bone. In ACTIVExtend, women who finished ACTIVE took alendronate for up to 24 months; over 43 months, 0.9% of those who had started on abaloparatide had a new spine fracture against 5.6% of those who had started on placebo (randomised trial, extension) ⁷. In men, the ATOM trial found spine bone density rose 8.48% with abaloparatide against 1.17% with placebo over a year, with injection-site reactions, dizziness and headache among the commonest side effects (randomised trial) ⁸. In Japanese women and men, 78 weeks of abaloparatide raised spine density 12.5% more than placebo (randomised trial) ⁹.

Why there are two drugs from two hormones

Teriparatide copies parathyroid hormone itself; abaloparatide is modelled on PTH-related protein, a hormone made by many tissues that shares the same receptor. The 2025 review describes both as agonists of the same type 1 receptor (review) ¹. So far, the clearest measured difference between them is ACTIVE's lower rate of raised blood calcium with abaloparatide (randomised trial) ⁶. Whether the difference translates into fewer fractures is the open question the review flags.

Men with osteoporosis

Osteoporosis is often thought of as a women's disease, but men get it too, and the trial evidence for men is newer. Abaloparatide's label now covers men at high fracture risk (dataset) ², supported by the ATOM trial's bone-density results in men aged 40 to 85 (randomised trial) ⁸. Bone-density trials in men are smaller than the fracture trials in women, so the fracture benefit in men is inferred from density changes rather than measured directly.

How the two compare

No randomised trial has been powered to compare fracture rates between them. In real-world insurance data on matched women over 50, hip fractures over 18 months occurred in 1.1% on abaloparatide against 1.4% on teriparatide (hazard ratio 0.83), and non-spine fractures in 4.4% against 5.0% (observational study) ¹⁰. Observational comparisons can be biased by who gets which drug, so the honest summary is that both work, abaloparatide caused less hypercalcaemia in ACTIVE (randomised trial) ⁶, and the choice often comes down to cost, insurance and practical factors. Our entries on teriparatide and abaloparatide give the details.

What the specialists conclude

A 2025 review by an international group of osteoporosis specialists summarised the field: both drugs increase bone density at the spine and hip, both reduce spine and non-spine fractures in randomised trials, their side effects are usually transient, and no osteosarcoma risk has been seen in extensive human studies. It noted that ACTIVE suggested slightly greater effect for abaloparatide on major osteoporotic fractures as an exploratory end point, and that an observational study suggested the same for hip fracture, while stressing that these differences need further research (review) ¹. The authors also judged both drugs cost-effective. The review's authors declared extensive industry ties, which is common in this field and worth knowing when reading its conclusions.

Side effects in the trials

In the Fracture Prevention Trial, side effects were minor, mainly occasional nausea and headache (randomised trial) ³. Abaloparatide's commonest side effects in men included injection-site reactions, dizziness and headache (randomised trial) ⁸, and in ACTIVE it caused raised blood calcium less often than teriparatide (randomised trial) ⁶. The 2025 review describes side effects as usually transient (review) ¹. The full lists, and the precautions about who should not take them, are on each drug's label and in our entries.

Building bone versus slowing loss

Most osteoporosis medicines, such as bisphosphonates, work by slowing the cells that break bone down, preserving what is there. Teriparatide and abaloparatide add new bone, and VERO showed what that difference can mean in people with severe disease: fewer new spine fractures than with risedronate over two years (randomised trial) ⁵. The usual approach is a course of a bone builder followed by a drug that preserves the gain, which is what ACTIVExtend tested with alendronate after abaloparatide (randomised trial, extension) ⁷.

ACTIVExtend's low fracture rate over 43 months came from that sequence, not from abaloparatide alone (randomised trial, extension) ⁷, which is one reason treatment is planned as a whole by a specialist rather than started and stopped casually.

The osteosarcoma story

Teriparatide carried a boxed warning for years because of rats. In a long-term study, rats given teriparatide at 30 µg/kg a day for 20 or 24 months, most of their lives, developed more bone tumours, including osteosarcoma; at 5 µg/kg started in adult rats, no tumours appeared even after 20 months, though bone mass still rose (animal study) ¹¹. Dose and duration mattered most.

Forteo was approved with a boxed warning, a two-year lifetime limit and a requirement to study cancer risk in people (review) ⁴. The US Osteosarcoma Surveillance Study, run from 2003, identified osteosarcoma cases through cancer registries: three patients had used teriparatide against about 4.17 expected from background rates, a standardised incidence ratio of 0.72 (surveillance study) ¹². Claims-linkage studies found no increase either, and in 2020 the label was updated: the boxed warning was removed and the two-year lifetime limit revised (review) ⁴.

The episode is a model of how a drug's risk should be handled: a signal in animals, caution in the label, and a dedicated study in people that eventually settled the question.

Where they did not help

These drugs build bone, but that does not mean they fix every bone problem. In osteogenesis imperfecta, brittle bone disease, two years of teriparatide followed by zoledronic acid in 349 adults raised bone density significantly but fracture rates were the same as with standard care (36.9% against 36.4%) (randomised trial) ¹³. Fracture healing is another limit, covered in the next section.

Why 'it builds bone' does not mean 'it heals breaks'

It seems natural that a bone-building drug would speed up the healing of a fracture, and the idea has been tested more than once. The results so far are disappointing. In 35 patients averaging 82 years old with pelvic fractures, three months of teriparatide did not improve healing on CT compared with placebo (50% against 53% healed), though physical performance improved on some measures (randomised trial) ¹⁴. In 40 women with fractures of the upper arm, four weeks of teriparatide made no significant difference to pain, painkiller use, function or the X-ray signs of healing (randomised trial) ¹⁵.

These are small trials, so a modest benefit cannot be ruled out, but they show why the approved uses are about preventing future fractures in osteoporosis, not repairing a break that has already happened. That distinction is worth remembering whenever a peptide is marketed for 'bone healing'.

Pills and patches

Daily injections are a barrier, and work on other routes continues. An oral PTH(1-34) tablet raised bone formation markers and spine density by 2.7% over six months at its highest dose in 161 women (randomised trial) ¹⁶. An experimental abaloparatide skin patch raised spine density 7.14% against 10.86% with the injection over a year in 511 women, missing its non-inferiority target (randomised trial) ¹⁷. Neither is approved, but both show that the field is trying to make bone building easier to take, which could make treatment easier for people who find a daily injection a real burden, if a future version proves as effective.

Research peptides sold for bones

Peptides such as BPC-157 and TB-500 are often marketed online for bone and joint healing on the strength of animal studies. Set against teriparatide and abaloparatide, the contrast is the point of this article: the approved bone peptides have randomised fracture trials in thousands of people, head-to-head comparisons and a decade and a half of cancer surveillance; the research peptides have none of these. Bone is a tissue where claims are easy to test properly, because fractures and bone density can be counted, and no research peptide sold online has been put through that test. Our article on tendon and ligament peptides covers what those compounds' evidence actually is.

Who these drugs are for

Both are approved for people at high risk of fracture, typically those who have already had a fragility fracture or have very low bone density (dataset) ². They are prescribed by specialists, given daily by injection for a limited period and usually followed by a drug that preserves the new bone, as ACTIVExtend illustrates (randomised trial, extension) ⁷. Anyone with osteoporosis should discuss which treatment fits their fracture risk with their doctor, including whether a bone builder or a drug that slows bone loss should come first, and what the plan is once the bone builder's course ends.

A short timeline

• 2001: the Fracture Prevention Trial shows teriparatide cuts new spine fractures by about two-thirds, after being stopped early because of a rat finding (randomised trial) ³.
• 2004: a long-term rat study shows tumours depend on high dose and near-lifetime treatment, with a no-effect dose that still builds bone (animal study) ¹¹.
• 2016: ACTIVE shows abaloparatide reduces spine and non-spine fractures against placebo (randomised trial) ⁶; Tymlos follows in 2017 (dataset) ².
• 2018: VERO shows teriparatide beats risedronate on new spine fractures (randomised trial) ⁵.
• 2020: teriparatide's boxed warning is removed after human surveillance (review) ⁴.
• 2022 to 2025: abaloparatide's evidence extends to men (randomised trial) ⁸, and oral and patch versions are tested (randomised trial) ¹⁷.

Questions to ask your doctor

• Is my fracture risk high enough that a bone-building drug makes sense before a bisphosphonate or similar?
• How long would I take it, and what would follow it to keep the new bone?
• Which of the two suits me, and what does my insurance cover?
• What side effects should I watch for, and will my calcium be checked?

Quick glossary

• Anabolic: builds bone, as these two drugs do.
• Antiresorptive: slows bone breakdown, as bisphosphonates do.
• PTH1R: the receptor both drugs activate.
• Hypercalcaemia: a raised blood calcium, less common with abaloparatide in ACTIVE.
• Osteosarcoma: a rare bone cancer, seen in rats at high lifetime doses and not increased in human surveillance.

How it adds up (as of October 5, 2026)

Teriparatide and abaloparatide are approved peptide drugs that build bone. Teriparatide cut new spine fractures from 14% to 5% in its pivotal trial and beat risedronate head to head; abaloparatide reduced spine and non-spine fractures against placebo with less hypercalcaemia than teriparatide. Teriparatide's osteosarcoma warning, based on high-dose lifetime rat studies, was removed in 2020 after 15 years of human surveillance found no increase. They do not help every bone problem: they did not prevent fractures in brittle bone disease or speed fracture healing in small trials. Research peptides sold for bones have nothing comparable behind them.

Frequently asked questions

Do teriparatide and abaloparatide build bone?

Yes. Both activate the parathyroid hormone receptor in daily pulses, which stimulates bone formation more than bone removal.

How much do they reduce fractures?

In its pivotal trial, teriparatide 20 µg cut new spine fractures from 14% to 5% (RR 0.35); abaloparatide reduced spine and non-spine fractures against placebo in ACTIVE.

Does teriparatide cause bone cancer?

Rats given high doses for most of their lives developed osteosarcoma, but 15 years of human surveillance found no increase, and FDA removed the boxed warning in 2020.

Which is better, teriparatide or abaloparatide?

No trial has been powered to compare their fracture rates. Abaloparatide caused less hypercalcaemia in ACTIVE (3.4% vs 6.4%); real-world data suggest similar results.

Can peptides like BPC-157 help osteoporosis?

There are no human fracture trials for research peptides like BPC-157; the approved bone peptides have trials in thousands of people.

Related on Grey Peptides

• Teriparatide
• Abaloparatide
• Every FDA-approved peptide drug
• Tendon and ligament peptides

Sources

1. Fuggle, N., et al. (2025). Parathyroid hormone receptor agonists in the management of osteoporosis. Nat Rev Rheumatol, 21(10), 599-611. PMID: 40790089
2. Grey Peptides dataset rows for teriparatide (Forteo and follow-on products on Drugs@FDA, read September 30, 2026) and abaloparatide (Tymlos, NDA 208743, first approved April 28, 2017; postmenopausal women and men with osteoporosis at high fracture risk; Drugs@FDA and label, read October 2, 2026).
3. Neer, R. M., et al. (2001). Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med, 344(19), 1434-41. PMID: 11346808
4. Krege, J. H., et al. (2022). Teriparatide and Osteosarcoma Risk: History, Science, Elimination of Boxed Warning, and Other Label Updates. JBMR Plus, 6(9), e10665. PMID: 36111201
5. Kendler, D. L., et al. (2018). 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, 391(10117), 230-240. PMID: 29129436
6. Miller, P. D., et al. (2016). Effect of Abaloparatide vs Placebo on New Vertebral Fractures in Postmenopausal Women With Osteoporosis: A Randomized Clinical Trial. JAMA, 316(7), 722-33. PMID: 27533157
7. Bone, H. G., et al. (2018). ACTIVExtend: 24 Months of Alendronate After 18 Months of Abaloparatide or Placebo for Postmenopausal Osteoporosis. J Clin Endocrinol Metab, 103(8), 2949-2957. PMID: 29800372
8. Czerwinski, E., et al. (2022). The Efficacy and Safety of Abaloparatide-SC in Men With Osteoporosis: A Randomized Clinical Trial. J Bone Miner Res, 37(12), 2435-2442. PMID: 36190391
9. Matsumoto, T., et al. (2022). Abaloparatide Increases Lumbar Spine and Hip BMD in Japanese Patients With Osteoporosis: The Phase 3 ACTIVE-J Study. J Clin Endocrinol Metab, 107(10), e4222-e4231. PMID: 35977548
10. Tabatabai, L., et al. (2025). Comparative Effectiveness of Abaloparatide and Teriparatide in Women 50 Years of Age and Older: Update of a Real-World Retrospective Analysis. Endocr Pract, 31(2), 159-168. PMID: 39551187
11. Vahle, J. L., et al. (2004). Bone neoplasms in F344 rats given teriparatide [rhPTH(1-34)] are dependent on duration of treatment and dose. Toxicol Pathol, 32(4), 426-38. PMID: 15204966
12. Gilsenan, A., et al. (2021). Teriparatide Did Not Increase Adult Osteosarcoma Incidence in a 15-Year US Postmarketing Surveillance Study. J Bone Miner Res, 36(2), 244-251. PMID: 32990990
13. Hald, J. D., et al. (2026). Teriparatide Plus Zoledronic Acid for Osteogenesis Imperfecta: A Randomized Clinical Trial. JAMA, 336(2), 116-124. PMID: 42133304
14. Nieves, J. W., et al. (2022). Teriparatide and pelvic fracture healing: a phase 2 randomized controlled trial. Osteoporos Int, 33(1), 239-250. PMID: 34383100
15. Johansson, T. (2016). PTH 1-34 (teriparatide) may not improve healing in proximal humerus fractures. A randomized, controlled study of 40 patients. Acta Orthop, 87(1), 79-82. PMID: 26179771
16. Tripto-Shkolnik, L., et al. (2024). 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, 39(6), 672-682. PMID: 38578978
17. Lewiecki, E. M., et al. (2023). Efficacy and Safety of Transdermal Abaloparatide in Postmenopausal Women with Osteoporosis: A Randomized Study. J Bone Miner Res, 38(10), 1404-1414. PMID: 37417725

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. 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.