Parathyroid hormone (1-34) (human): Precision Tool for Calcium Homeostasis and Bone Research

Executive Summary: Parathyroid hormone (1-34) (human), also known as PTH (1-34), is a synthetic peptide fragment corresponding to the amino-terminal region of endogenous human parathyroid hormone. It acts as a selective agonist for PTH1R and PTH2R, triggering potent cAMP and inositol phosphate signaling in target tissues (Huang et al., 2025). With a molecular weight of 4117.72 Da, it facilitates rapid calcium mobilization from bone, upregulates renal reabsorption of calcium and magnesium, and enhances intestinal calcium uptake via vitamin D activation (APExBIO). In vivo, it produces dose-dependent increases in bone mass in Fisher 344 rats. Its high solubility in DMSO and water, but not ethanol, ensures versatility in experimental protocols. Supplied by APExBIO at ≥97.8% purity, this reagent is a cornerstone in translational bone and renal disease modeling.

Biological Rationale

The parathyroid hormone (PTH) axis is essential for maintaining serum calcium levels within a narrow physiological range (2.1–2.6 mmol/L in humans). PTH (1-34) represents the biologically active domain of the 84-amino acid native hormone. Endogenous PTH is secreted by the chief cells of the parathyroid glands in response to hypocalcemia. The (1-34) fragment retains full receptor agonism, making it valuable for both mechanistic and translational studies (APExBIO).

In bone, PTH (1-34) regulates osteoblast and osteoclast activity, promoting bone remodeling and mineral homeostasis. In the kidney, it acts on distal tubules and the thick ascending limb to enhance reabsorption of calcium and magnesium ions, while stimulating 1-α-hydroxylase activity for vitamin D synthesis. In the intestine, activated vitamin D increases calcium absorption, completing a tightly regulated feedback loop. These functions are conserved across vertebrates and underlie the rationale for employing PTH (1-34) in experimental models of bone metabolism, kidney physiology, and calcium signaling disorders.

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

PTH (1-34) binds with high affinity to the parathyroid hormone 1 receptor (PTH1R) and, to a lesser extent, PTH2R. Both receptors are G protein-coupled receptors (GPCRs) expressed in bone, kidney, and cardiovascular tissues. Upon ligand engagement, PTH1R undergoes conformational change, activating Gαs and Gαq pathways. This results in rapid elevation of intracellular cAMP and inositol phosphate synthesis, respectively.

• cAMP pathway: PTH (1-34) stimulates adenylate cyclase, raising cAMP with an IC₅₀ of 0.22 nM in HEK293 cells expressing PTH1R (APExBIO).
• Inositol phosphate pathway: Parallel activation of phospholipase C increases IP₃ and DAG, modulating calcium release from intracellular stores.

Downstream, these cascades drive genomic and non-genomic responses: stimulation of RANKL and OPG expression in osteoblasts, modulation of calcium transporter expression in renal tubules, and induction of 1,25(OH)₂D synthesis in the proximal tubule (Huang et al., 2025).

Evidence & Benchmarks

• PTH (1-34) increases cAMP production in human kidney 293 cells transfected with PTH1R, with an IC₅₀ of 0.22 nM (APExBIO product sheet: link).
• Subcutaneous administration (10 or 40 μg/kg/day) in male Fisher 344 rats produces dose- and time-dependent increases in trabecular and cortical bone mass (APExBIO).
• In advanced kidney assembloid models, PTH/PTHrP receptor signaling enables precise manipulation of renal epithelial cell maturation and function (Huang et al., 2025).
• The peptide is soluble at ≥399.3 mg/mL in DMSO and ≥19.88 mg/mL in water, allowing for high-concentration stock solutions (APExBIO: link).
• Supplied at ≥97.8% purity, ensuring minimal batch-to-batch variation and high reproducibility (APExBIO: link).

Applications, Limits & Misconceptions

Parathyroid hormone (1-34) (human) is widely used as a research tool in multiple domains:

• Bone metabolism research: It serves as a gold standard for inducing bone formation and remodeling in cell culture and animal models (see also). This article provides detailed mechanism-of-action data not found in previous reviews.
• Osteoporosis model development: PTH (1-34) is used to model anabolic and catabolic phases of bone turnover, supporting drug screening and mechanistic studies.
• Kidney and organoid research: In advanced kidney assembloid systems, PTH (1-34) modulates epithelial and transporter maturation, supporting high-fidelity disease modeling (contrast: this article expands on scenario-based applications by adding recent organoid integration data).
• cAMP signaling pathway studies: Its predictable agonism allows for precise dissection of GPCR-mediated signal transduction (contrast: this updates recent insights with new benchmarks for cAMP potency).

Common Pitfalls or Misconceptions

• PTH (1-34) is not a full-length hormone; it lacks the C-terminal domain, which may modulate certain cell surface interactions.
• It is not suitable for clinical or diagnostic use; research-only, non-GMP grade.
• Chronic, continuous exposure may produce catabolic bone effects, in contrast to intermittent, pulsatile dosing which is anabolic.
• Peptide is insoluble in ethanol, limiting solvent choice.
• Long-term storage of diluted solutions (>1 week at 4°C or -20°C) can result in degradation and loss of activity.

Workflow Integration & Parameters

PTH (1-34) (human) is supplied as a lyophilized solid by APExBIO (SKU: A1129), stored desiccated at -20°C. For laboratory use, reconstitute in DMSO or water to the required stock concentration (up to 399.3 mg/mL in DMSO). Prepare aliquots for single-use to avoid repeated freeze-thaw cycles. Typical working concentrations range from 0.1 nM to 1 μM, depending on assay sensitivity and cell type. For in vivo studies, dosing regimens (e.g., 10–40 μg/kg/day, subcutaneous) should be optimized according to species and model endpoint (see also: this article adds solubility and storage guidelines for robust assay reproducibility).

For advanced organoid and assembloid systems, PTH (1-34) can be added to culture media to modulate differentiation and transporter expression, as recently demonstrated in kidney progenitor assembloid platforms (Huang et al., 2025).

Conclusion & Outlook

Parathyroid hormone (1-34) (human) is a powerful, well-validated tool for dissecting calcium homeostasis and bone remodeling pathways. Its predictable effects on PTH1R and robust cAMP generation underpin its widespread adoption in osteoporosis, nephrology, and organoid research. Continued integration into high-fidelity human assembloid and disease models will further clarify its translational relevance. For further details and ordering information, see the APExBIO product page.