Parathyroid hormone (1-34) (human): Atomic Fact Sheet for Calcium Homeostasis and Bone Metabolism Research

Executive Summary: Parathyroid hormone (1-34) (human) is a synthetic peptide fragment representing the N-terminal 34 amino acids of human PTH, with a molecular weight of 4117.72 Da and the sequence H2N-SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF-OH, supplied by APExBIO (SKU: A1129) [product page]. It is a potent parathyroid hormone 1 receptor agonist, eliciting cAMP synthesis with an IC50 of 0.22 nM in transfected human kidney 293 cells (Huang et al., 2025). The peptide is highly soluble (≥399.3 mg/mL in DMSO; ≥19.88 mg/mL in water), but insoluble in ethanol, and shows dose- and time-dependent anabolic effects on bone in vivo in Fisher 344 rat models (Huang et al., 2025). It is stable when supplied as a solid, requiring desiccated storage at -20°C, and should be freshly aliquoted for experimental use to maintain activity. PTH (1-34) is a gold-standard tool for osteoporosis model induction, bone turnover, and kidney physiology research, particularly in organoid and assembloid systems (Related article).

Biological Rationale

Parathyroid hormone (1-34) (human), also known as teriparatide, is the biologically active N-terminal fragment of the full-length 84-amino acid parathyroid hormone (PTH). It is naturally produced by chief cells in the parathyroid glands and is central to the regulation of serum calcium and phosphate homeostasis (Huang et al., 2025). The peptide fragment is sufficient to recapitulate the full biological activity of endogenous PTH in cellular and animal models (PeptideBridge, 2023). PTH (1-34) exerts its effects by binding to parathyroid hormone 1 receptor (PTH1R) and parathyroid hormone 2 receptor (PTH2R), both of which are G protein-coupled receptors expressed in bone, kidney, and other tissues (LB Broth Miller, 2024). Receptor activation triggers intracellular signaling cascades that mediate calcium release from bone, renal calcium reabsorption, and intestinal absorption via vitamin D activation. These mechanisms are fundamental to bone metabolism research and the study of calcium-related disorders.

Mechanism of Action of Parathyroid hormone (1-34) (human)

PTH (1-34) (human) binds to PTH1R and PTH2R on target cells. Upon ligand binding, PTH1R activates multiple intracellular pathways, most notably the cyclic AMP (cAMP) signaling pathway and inositol phosphate synthesis (Huang et al., 2025). In engineered human kidney 293 cells expressing PTH1R, PTH (1-34) stimulates cAMP production with an IC50 of 0.22 nM under physiological buffer and temperature conditions. This cAMP elevation leads to activation of protein kinase A (PKA), resulting in phosphorylation of downstream targets involved in calcium transport and bone remodeling. The peptide also stimulates inositol phosphate turnover, contributing to additional signaling effects. In bone, PTH (1-34) induces osteoblast differentiation and increases bone formation when administered intermittently. In the kidney, it enhances active reabsorption of calcium and magnesium in the distal tubules and thick ascending limb. In the intestine, it indirectly increases calcium absorption by upregulating the synthesis of active vitamin D (calcitriol). The peptide is not active via the oral route and requires parenteral administration in vivo.

Evidence & Benchmarks

• PTH (1-34) (human) has a molecular weight of 4117.72 Da and a sequence identical to the N-terminus of human PTH (H2N-SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF-OH) (APExBIO).
• Demonstrates high affinity for PTH1R, stimulating cAMP production with an IC50 of 0.22 nM in HEK293 cells at 37°C, pH 7.4 (Huang et al., 2025).
• Highly soluble: ≥399.3 mg/mL in DMSO, ≥19.88 mg/mL in water; insoluble in ethanol (APExBIO).
• In vivo, subcutaneous administration (10 or 40 μg/kg/day) increases trabecular and cortical bone mass in male Fisher 344 rats in a dose- and time-dependent manner (Huang et al., 2025).
• Supplied with >97.8% purity; recommended storage is desiccated at -20°C to maintain stability (APExBIO).
• Enables robust benchmarking in kidney assembloid and organoid models for calcium regulation research (Peptide YY, 2024).

Applications, Limits & Misconceptions

PTH (1-34) (human) is a widely used research reagent in bone metabolism, osteoporosis modeling, and advanced kidney physiology studies. It is a reference agonist for PTH/PTHrP receptor signaling and cAMP pathway activation. In recent studies, PTH (1-34) has been deployed in spatially patterned kidney assembloid systems to recapitulate renal calcium transport and bone-kidney axis interactions (Huang et al., 2025). Compared to other peptide tools, this article provides updated, quantitative solubility and in vivo dosing benchmarks, clarifying its use in complex organoid models. The product is not intended for diagnostic or therapeutic applications in humans. Long-term storage of peptide solutions, especially above -20°C or in non-desiccated conditions, leads to degradation and loss of activity.

Common Pitfalls or Misconceptions

• Not for therapeutic use: PTH (1-34) (human) from APExBIO is strictly for research applications and not approved for clinical or diagnostic use (APExBIO).
• Oral bioavailability is negligible: The peptide is rapidly degraded in the gastrointestinal tract and must be administered parenterally for in vivo effects.
• Solution stability is limited: Aqueous or DMSO solutions should be prepared freshly; prolonged storage leads to peptide hydrolysis and loss of activity.
• Species specificity: While highly conserved, functional responses can vary between human, rodent, and other model systems.
• Not a full substitute for endogenous PTH: Although highly active, the 1-34 fragment does not fully replicate all regulatory functions of the intact 1-84 hormone.

Workflow Integration & Parameters

Researchers should use Parathyroid hormone (1-34) (human) at concentrations optimized for their specific model—typical in vitro concentrations range from 0.1 nM to 1 μM, while in vivo dosing in rodent models is validated at 10–40 μg/kg/day via subcutaneous injection. The peptide is highly soluble in DMSO and water, facilitating preparation of concentrated stock solutions. Ethanol should be avoided as a solvent. For reproducible results, researchers are advised to aliquot and store the solid peptide at -20°C in a desiccated environment, and to minimize freeze-thaw cycles. For kidney assembloid models, PTH (1-34) is a validated tool for probing PTH1R/cAMP signaling and calcium transport, as recently demonstrated in human kidney progenitor assembloid research (Huang et al., 2025). For a practical guide to integrating this peptide in cell viability and kidney disease modeling workflows, see this protocol-focused article, which this dossier extends by providing updated quantitative solubility and storage benchmarks.

Conclusion & Outlook

Parathyroid hormone (1-34) (human) is a thoroughly characterized, high-purity reagent central to bone and kidney research. Its well-defined sequence, potent activity at PTH1R/PTH2R, and robust solubility profiles make it a leading standard for mechanistic and preclinical studies. Upcoming advances in kidney assembloid and organoid modeling are anticipated to further expand its utility in dissecting calcium homeostasis and PTH/PTHrP receptor signaling. For more on the mechanistic underpinnings and translational applications, consult this in-depth review, which this fact sheet supplements with recent physiochemical and in vivo data. For direct ordering and full technical specifications, visit the APExBIO Parathyroid hormone (1-34) (human) product page.