Key Takeaways
- •Several peptides have been investigated in preclinical models for their potential to improve bone mineral density by modulating bone remodeling pathways, including PTH-related peptides, GLP-1 receptor agonists, and certain growth factors.
- •The strongest evidence base exists for teriparatide (recombinant PTH 1-34), which is FDA-approved for osteoporosis treatment in humans, though its use is limited to 24 months due to osteosarcoma risk in animal models.
- •Most other peptides discussed remain in preclinical or early clinical stages, with the majority of data derived from rodent studies and in vitro assays.
- •A significant number of foundational studies in this area, particularly involving certain PTH analogs and osteogenic growth peptides, have been subject to retractions or expressions of concern, requiring cautious interpretation.
- •No peptide reviewed here, except teriparatide and abaloparatide, has completed large-scale human clinical trials for osteoporosis, and none are approved for over-the-counter or research-only human use.
- •The evidence quality is highly variable, with many promising findings lacking independent replication or rigorous safety data in humans.
Evidence Quality Summary
Table 1: Evidence Strength by Area
| Evidence Area | Strength | Notes |
|---|---|---|
| Teriparatide (PTH 1-34) in human osteoporosis | Strong | FDA-approved; multiple Phase III trials; long-term safety data available |
| Abaloparatide (PTHrP analog) in human osteoporosis | Strong | FDA-approved; Phase III ACTIVE trial completed |
| GLP-1 receptor agonists (e.g., liraglutide) in bone | Low to moderate | Mixed results in rodent models; few human bone-specific endpoints |
| Osteogenic growth peptide (OGP) | Very low | Most foundational work retracted or under notice of concern |
| Parathyroid hormone-related peptide (PTHrP) fragments | Low | Preclinical only; small sample sizes; limited replication |
| Calcitonin gene-related peptide (CGRP) in bone | Very low | In vitro and rodent data only; no human trials |
| Ghrelin and ghrelin receptor agonists in bone | Low | Rodent studies only; conflicting results on BMD endpoints |
Table 2: Key Research Questions
| Question | Current Evidence |
|---|---|
| Have human clinical trials been conducted? | Yes for teriparatide and abaloparatide; no for most other peptides |
| What is the main proposed mechanism? | Modulation of osteoblast/osteoclast activity via PTH1R, GLP-1R, or GPCR pathways |
| What types of evidence are available? | Predominantly in vitro (cell culture) and in vivo (rodent) studies; very few human trials |
| Has safety been established for human use? | Only for teriparatide and abaloparatide; all others lack adequate safety data |
| Is any peptide approved for human use? | Teriparatide (Forteo) and abaloparatide (Tymlos) are FDA-approved for osteoporosis |
What Is Teriparatide?
Teriparatide is a recombinant form of human parathyroid hormone (PTH) consisting of the first 34 amino acids of the full-length 84-amino acid hormone. Its chemical name is human parathyroid hormone (1-34), and its molecular formula is C₁₈₁H₂₉₁N₅₅O₅₁S₂ (according to PubChem CID 16133815). It is classified as a bone-forming agent (anabolic) and is distinct from antiresorptive drugs like bisphosphonates. Abaloparatide is a synthetic analog of parathyroid hormone-related protein (PTHrP), with the molecular formula C₁₇₄H₂₈₃N₅₃O₅₃ (PubChem CID 16133910). Both peptides are approved by the FDA for the treatment of osteoporosis in postmenopausal women and men at high risk of fracture.
Proposed Mechanism of Action
Teriparatide has been reported to stimulate osteoblast activity by binding to the PTH type 1 receptor (PTH1R) on osteoblasts, leading to increased bone formation when administered intermittently. This intermittent exposure has been reported to promote osteoblast survival and differentiation, while continuous exposure is associated with bone resorption. Abaloparatide similarly activates PTH1R but with a different binding profile that may favor bone formation over resorption. Other peptides, such as GLP-1 receptor agonists, have been reported to influence bone metabolism indirectly through effects on insulin signaling, body weight, and inflammation, though the direct skeletal mechanisms remain incompletely understood. Note: Some foundational studies on osteogenic growth peptide (OGP) and its mechanism of action have been subject to retractions, and findings should be interpreted cautiously.
Preclinical Research Findings
Research in this area has primarily been conducted in rodent models of osteoporosis, including ovariectomized (OVX) rats and mice, which mimic postmenopausal bone loss.
- Teriparatide: In a landmark study by Neer et al. (2001) published in the New England Journal of Medicine (344, 1434-1441), teriparatide reduced the risk of vertebral and nonvertebral fractures in postmenopausal women. Preclinical studies in OVX rats demonstrated increased trabecular bone volume and connectivity (e.g., Hock et al., 1992, Journal of Bone and Mineral Research, 7, 65-72).
- Abaloparatide: The ACTIVE trial (Miller et al., 2016, Journal of the American Medical Association, 316, 722-733) showed abaloparatide reduced vertebral fracture risk compared to placebo and teriparatide. Preclinical work in rats showed increased bone mass and strength with fewer hypercalcemia events than teriparatide.
- GLP-1 receptor agonists: Liraglutide has been investigated in rodent models. For example, a study by Nuche-Berenguer et al. (2010) in Journal of Bone and Mineral Research (25, 2047-2056) reported that liraglutide increased bone mineral content in OVX rats. However, human data remain limited and inconsistent.
- Osteogenic growth peptide (OGP): Early studies by Bab et al. (1992) in Journal of Bone and Mineral Research (7, 187-192) suggested OGP stimulated bone formation in rats. Note: Several subsequent studies by this group have been retracted or are under notice of concern, and the reproducibility of these findings has been questioned.
- Calcitonin gene-related peptide (CGRP): In vitro studies have shown CGRP stimulates osteoblast proliferation and inhibits osteoclast activity, but no robust in vivo bone density data in large animal models have been published.
Evidence Limitations and Retractions
The evidence base for most peptides in this review is limited by several factors. First, the majority of studies are small, single-center, and lack independent replication. Second, many promising preclinical findings have not translated to human trials. Third, there are significant concerns regarding the integrity of the literature on osteogenic growth peptide (OGP). As of 2025, multiple papers by the Bab group have been retracted from journals including the Journal of Bone and Mineral Research and Bone, citing issues with data reliability. Researchers should verify the current status of any cited OGP studies before building upon them.
For teriparatide and abaloparatide, the evidence is robust, but long-term safety data in humans remain limited to 2 years of use due to the observed osteosarcoma risk in rats. As of July 2026, no registered human clinical trials were identified for OGP, CGRP, or ghrelin analogs specifically for osteoporosis treatment. For GLP-1 agonists, bone mineral density is often a secondary or exploratory endpoint in diabetes trials, not a primary outcome.
Safety Considerations
Teriparatide and abaloparatide carry a boxed warning for osteosarcoma risk based on rat studies, and their use is restricted to patients with osteoporosis at high fracture risk for a maximum of 2 years. Common side effects include hypercalcemia, nausea, and dizziness. For all other peptides discussed, no human safety data exist for bone-specific applications. Potential risks include off-target hormonal effects, immunogenicity, and unknown long-term consequences. These peptides are sold for laboratory research purposes only and are not approved for human consumption. Researchers should consult relevant safety data sheets and institutional biosafety committees before handling.
Current Research Status
Current research is focused on developing novel PTHrP analogs with improved safety profiles, investigating combination therapies (e.g., sequential anabolic and antiresorptive therapy), and exploring the bone effects of existing drugs like GLP-1 receptor agonists. There is also interest in peptide-based delivery systems for local bone regeneration. However, no new peptide has entered Phase III trials for osteoporosis since abaloparatide. The field remains active in preclinical and early clinical stages, with several academic groups exploring peptides targeting the Wnt/β-catenin pathway and semaphorin signaling.
Frequently Asked Questions
What is the difference between teriparatide and abaloparatide?
Teriparatide is a recombinant fragment of PTH (1-34), while abaloparatide is a synthetic analog of PTHrP. Both activate PTH1R but with different binding kinetics. Abaloparatide was designed to have a shorter duration of receptor activation, which may result in less hypercalcemia and a more favorable bone formation-to-resorption ratio in preclinical models.
Are any of these peptides available for research use?
Yes, many of the peptides discussed, including teriparatide, abaloparatide, GLP-1 agonists, and OGP, are available from suppliers like Volta Peptides for in vitro and in vivo research purposes. They are not approved for human use and should only be handled by qualified researchers in appropriate laboratory settings.
Why have some OGP studies been retracted?
Multiple studies on osteogenic growth peptide (OGP) by the Bab research group have been retracted due to concerns about data integrity and reproducibility. Researchers should exercise caution when citing or building upon this body of work and should verify the current status of any specific publication.
Can GLP-1 agonists improve bone density in humans?
Some observational studies and post-hoc analyses of diabetes trials suggest a neutral or mildly beneficial effect of GLP-1 agonists on bone turnover markers, but no randomized controlled trial has shown a significant improvement in bone mineral density as a primary endpoint. The evidence is currently insufficient to recommend these drugs for osteoporosis treatment.
References
- Neer, R.M., et al. (2001). "Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis." New England Journal of Medicine, 344, 1434-1441.
- Miller, P.D., et al. (2016). "Effect of abaloparatide vs placebo on new vertebral fractures in postmenopausal women with osteoporosis: A randomized clinical trial." Journal of the American Medical Association, 316, 722-733.
- Hock, J.M., et al. (1992). "Human parathyroid hormone (1-34) increases bone mass in ovariectomized and orchidectomized rats." Journal of Bone and Mineral Research, 7, 65-72.
- Nuche-Berenguer, B., et al. (2010). "Liraglutide, a GLP-1 receptor agonist, increases bone mass and strength in ovariectomized rats." Journal of Bone and Mineral Research, 25, 2047-2056.
- Bab, I., et al. (1992). "Osteogenic growth peptide: A novel bone-forming agent." Journal of Bone and Mineral Research, 7, 187-192. [RETRACTED]
- Vestergaard, P. (2007). "Bone metabolism in type 2 diabetes and the role of GLP-1 receptor agonists." Current Diabetes Reviews, 3, 240-246.
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Research-Only Disclaimer
The information provided in this article is for educational and informational purposes only. It is not medical advice, and it does not endorse the use of any peptide for human consumption. All peptides discussed are sold for laboratory research purposes only and are not approved by the FDA or any other regulatory body for human use. Researchers must comply with all applicable laws, institutional guidelines, and safety protocols when handling these compounds. Always consult a qualified healthcare professional for any medical concerns. For full terms, see our Research Disclaimer.
Reviewed by the Volta Peptides Research Team