Bone-building parathyroid hormone fragment: bovine version (PTH 1-34)
A lab research form of the natural hormone that tells bone-building cells to get to work; differs slightly from the human drug Forteo and is used only as a research tool.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Parathyroid hormone (PTH) is the body's primary regulator of calcium and bone turnover — a hormone released by the parathyroid glands that tells bone-building cells to get to work. The first 34 amino acids at its N-terminus (PTH 1-34) carry the full biological activity of the intact 84-residue hormone. This card covers the bovine form of PTH (1-34), the sequence used extensively in early laboratory research and still used as a research tool today. It differs from the human clinical drug teriparatide (hPTH 1-34, sold as Forteo/Forsteo) at six positions across the 34-residue stretch, with the most notable difference being alanine rather than serine at the N-terminal position 1 (Potts and colleagues, PNAS 1972). Both forms bind the same receptor — PTH type 1 receptor (PTH1R) — and share essentially the same mechanism of action, which is why bovine PTH (1-34) remains a standard pharmacological reference compound and research tool.
History
Interest in the parathyroid glands' ability to stimulate bone formation dates to the 1920s, when extracts from bovine parathyroid tissue were shown to increase bone acquisition in rodents. That observation lay largely dormant for nearly half a century. In 1970, Brewer and Ronan determined the complete 84-residue amino acid sequence of bovine PTH (Brewer and Ronan, PNAS 1970). The following year, the Potts group synthesized the N-terminal 1-34 fragment and demonstrated in bioassays that it was as potent as the intact hormone for inducing PTH1R-mediated biological responses — establishing the concept that the active pharmacophore resided entirely within this short fragment. In the 1970s, largely driven by the work of British pharmacologist John Parsons, researchers showed that single daily injections of PTH (1-34) dramatically increased bone mass in multiple mammalian species, reframing the hormone as a potential bone-building agent rather than purely a calcium regulator (Marcus 2011). Human PTH 1-34 sequence was reported in PNAS in 1972 (Potts and colleagues). The clinical development that followed culminated in FDA approval of recombinant human PTH (1-34) — teriparatide — in 2002, and EMA approval as Forsteo in 2003. Bovine PTH (1-34) underpins much of the foundational pharmacology that enabled that trajectory.
What it does
Binding of PTH (1-34) to PTH1R on osteoblasts and renal tubular cells triggers new bone formation when exposure is intermittent — essentially, a short daily pulse of the hormone shifts the balance between bone-building and bone-resorbing cells in favor of formation. This is the key biological insight behind teriparatide: continuous PTH elevation (as in primary hyperparathyroidism) causes net bone loss through sustained osteoclast activation, but brief daily exposure activates osteoblasts and expands the "anabolic window" during which bone is deposited faster than it is removed (Lee and colleagues 2009; Sato and colleagues 2021). PTH (1-34) also acts on the kidney to increase calcium reabsorption and stimulate production of activated vitamin D (1,25-dihydroxyvitamin D), which in turn enhances intestinal calcium absorption (Gardella and colleagues 2015). The downstream result — at the tissue level — is an increase in trabecular bone volume, trabecular thickness, and cortical bone area (Sato and colleagues 2021).
Evidence
- Human (teriparatide, the human analog): The landmark Fracture Prevention Trial (Neer and colleagues 2001), a randomized, double-blind study in 1,637 postmenopausal women with prior vertebral fractures, found that 20 µg/day teriparatide over approximately 21 months reduced the relative risk of new vertebral fractures by 65% and nonvertebral fragility fractures by 53%, with lumbar spine BMD increasing by approximately 9.7% (StatPearls review; PMC11026046 systematic review). The Extended Forsteo Observational Study (ExFOS), a prospective multinational study in 1,454 patients with severe osteoporosis across eight European countries, documented a 49% decrease in the odds of clinical fractures in the 18–24 month period compared with the first 6 months of treatment, with back pain decreasing by 23 mm on a visual analogue scale by month 24 (ExFOS, PMC4960288). In glucocorticoid-induced osteoporosis, teriparatide outperformed alendronate on BMD gain in an 18-month randomized trial (Saag and colleagues 2007, NEJM).
- Animal (bovine PTH 1-34): The bovine fragment was the primary research tool in preclinical models that established the intermittent-dosing anabolic effect. Single-daily-injection studies in rats and other species demonstrated significant increases in trabecular bone volume and density, and established the dose-response relationships that informed clinical development (Marcus 2011).
- In vitro: PTH (1-34) activates PTH1R via Gαs-mediated adenylate cyclase (raising intracellular cAMP) and Gq-mediated protein kinase C, with downstream effects including upregulation of IGF-1 and FGF-2, downregulation of the Wnt-pathway antagonist sclerostin, and increased Runx2 expression driving osteoblast differentiation (Sutkeviciute and colleagues 2019; StatPearls). Comparative in vitro work shows that bovine PTH (1-34) and human PTH (1-34) engage PTH1R with equivalent initial signaling kinetics (Sato and colleagues 2021).
Known effects
- Increased bone mineral density (spine, hip) — well-established in human clinical trials (teriparatide analog)
- Reduced vertebral fracture risk — Phase III evidence (teriparatide, Neer 2001)
- Reduced nonvertebral fracture risk — Phase III evidence (teriparatide, Neer 2001)
- Improved trabecular microarchitecture — Preclinical and imaging studies
- Calcium and vitamin D metabolism modulation — Mechanistic, mediated via PTH1R on renal tubular cells
- Back pain reduction — Observational evidence (ExFOS, postmenopausal severe osteoporosis)
Safety signals
Reported from teriparatide (human PTH 1-34) clinical trials and postmarketing experience; the same signals are expected for bovine PTH (1-34) given shared mechanism and receptor. Common adverse effects include nausea, headache, dizziness, and leg cramps. Transient hypercalcemia occurs and is more frequent at higher doses; persistent hypercalcemia requiring intervention was observed in approximately 3% of patients at the 20 µg dose in phase III trials (StatPearls). Orthostatic hypotension, particularly shortly after injection, has been reported.
A boxed warning about osteosarcoma risk was attached to teriparatide at FDA approval in 2002, based on preclinical findings of osteosarcoma in rats treated at doses substantially higher than human therapeutic exposure. A mandated 15-year postmarketing surveillance study (2003–2016) identified 3 teriparatide-exposed osteosarcoma cases against an expected background of 4.17 — a standardized incidence ratio of 0.72 (90% CI 0.20–1.86) — indicating no elevation in risk. The FDA removed the osteosarcoma boxed warning in November 2020 (Krege and colleagues 2022, JBMR Plus). The current label retains guidance to avoid use in patients with pre-existing conditions that independently elevate osteosarcoma risk (Paget disease of bone, history of skeletal malignancy, prior ionizing radiation to the skeleton, open epiphyses in pediatric patients).
Regulatory status
- US (teriparatide, human form): Prescription-only. FDA-approved (2002) for postmenopausal osteoporosis at high fracture risk, for men with primary or hypogonadal osteoporosis at high fracture risk, and for glucocorticoid-induced osteoporosis. Osteosarcoma boxed warning removed November 2020; the prior 2-year lifetime use limitation was also lifted at that time.
- EU (teriparatide, human form): EMA-approved as Forsteo (2003) for osteoporosis in postmenopausal women and men at increased fracture risk. Multiple biosimilar approvals subsequently granted.
- Bovine PTH (1-34) as a research compound: Not approved for clinical use; used as a pharmacological reference standard and research reagent (e.g., NIBSC reference preparation 82/512).
- WADA: Teriparatide and PTH analogs are classified under S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) and are prohibited both in- and out-of-competition.
Mechanism
PTH (1-34) is a full agonist at PTH1R, a Class B GPCR that couples to both Gαs and Gαq G-proteins (Gardella and colleagues 2015; Sutkeviciute and colleagues 2019). Gαs coupling activates adenylyl cyclase, raising intracellular cAMP and activating protein kinase A (PKA); Gq coupling activates phospholipase C and protein kinase C (PKC). In osteoblasts, PKA-dependent signalling drives the anabolic program: IGF-1 and FGF-2 are upregulated, sclerostin (a Wnt-pathway suppressor) is downregulated enabling canonical Wnt/β-catenin signalling, and RANKL/OPG ratio changes initially favour bone formation over resorption during the brief daily signalling window (StatPearls; Sutkeviciute and colleagues 2019). The receptor exists in two primary conformations — R0 (ligand-stabilized, inactive G-protein state) and RG (pre-coupled to Gαs). Teriparatide has relatively higher affinity for R0, producing a longer-lasting cAMP signal; abaloparatide preferentially engages RG, producing a faster but briefer signal with a different bone resorption marker profile (Sato and colleagues 2021). The bovine sequence has an alanine at position 1 rather than serine, and differs at five additional positions across residues 7, 16, 22, 28, and 30; despite these differences, the two fragments engage PTH1R with comparable initial signalling kinetics and equivalent downstream anabolic effects in standard bioassays (Sato and colleagues 2021).
Related peptides
- Teriparatide (hPTH 1-34) — the human clinical form, approved for osteoporosis; differs from this bovine sequence at 6 residues including N-terminal Ser¹ vs Ala¹
- Abaloparatide — a PTHrP-derived PTH1R agonist with preferential RG-conformation engagement; FDA-approved for osteoporosis; see also the comparative signalling work in Sato and colleagues (2021)
- PTH (1-84) — the intact endogenous hormone of which this fragment represents the active N-terminal core
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does the slightly different bovine form of the bone-building hormone activate cells in a subtly different way than the approved human drug teriparatide?
If true, this could reveal a natural example of a 'biased' hormone that avoids some unwanted side effects, helping researchers design better osteoporosis treatments. It would matter most to patients who need long-term bone-building therapy with fewer risks.
If a patient's immune system starts blocking the human bone drug, could the slightly different bovine version still get through?
Some osteoporosis patients stop responding to teriparatide because their immune system attacks it. If bovine PTH 1-34 dodges those attacks while still building bone, it could offer a second-line treatment for people with few options, reducing fracture risk in a vulnerable group.
Could the slightly floppy end of the bovine hormone cause it to bind its receptor at a different speed than the human drug, even if the final grip is the same?
If true, it would explain subtle differences seen between bovine and human PTH in laboratory experiments and could guide the design of hormones that stick to bone receptors longer, potentially reducing how often patients need injections.
After the bovine hormone enters bone-building cells, does it keep sending its 'build bone' signal longer or shorter than the human drug?
If bovine PTH sustains its signal differently, it could help explain why some preclinical experiments give different results with bovine vs human hormone, and could point toward a design for a once-weekly bone drug instead of daily injections.
Does bovine PTH 1-34 skip over a second, related receptor that the human drug accidentally activates?
If bovine PTH 1-34 is cleaner in its targeting, it could be a better research tool for studying bone biology specifically, and its sequence differences might inspire safer drugs that avoid unwanted effects on the brain or pancreas.
Could combining the best parts of bovine and human PTH into one molecule create a stronger bone-building hormone?
A more potent hybrid could mean lower doses are needed to build bone, reducing the risk of side effects like high calcium in the blood. This could allow longer or safer treatment for the millions of people worldwide at risk of osteoporosis fractures.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8534017205238342 | openfold3-mlx |
| ranking score | 0.9710975885391235 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.855 | global PDE — lower = better |
| disorder | 0.316 | ! high disorder |
| chain pair ipTM (A, B) | 0.853 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 745s |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10507,
sequence = {AVSEIQFMHNLGKHLSSMERVEWLRKKLQDVHNF},
target = {pth1r},
author = {peptidemodel},
year = {2026},
status = {computed}
}