What does the Parathyroid Hormone, Intact (iPTH, PTH 1-84) test measure?

Why is Parathyroid Hormone, Intact (iPTH, PTH 1-84) measured?

Intact PTH is the definitive marker for parathyroid gland function and the central biochemical tool in hypercalcaemia and hypocalcaemia differential diagnosis. Its interpretation is inseparable from concurrent serum calcium — specifically ionised or albumin-corrected total calcium — as the PTH:calcium relationship is the diagnostic axis that localises the aetiology of calcium dysregulation to the parathyroid gland (PTH-dependent) or to extra-parathyroid mechanisms (PTH-independent). Elevated PTH with elevated calcium defines primary hyperparathyroidism — the most common cause of outpatient hypercalcaemia. Elevated PTH with low or normal calcium defines secondary hyperparathyroidism — driven by vitamin D deficiency, malabsorption, or chronic kidney disease stimulating compensatory PTH secretion to defend serum calcium. Suppressed PTH with elevated calcium defines PTH-independent (malignancy-associated, granulomatous, or drug-mediated) hypercalcaemia requiring a distinct investigative pathway. In Boston Heart Diagnostics' cardiovascular context, emerging evidence links chronically elevated PTH — even within or marginally above the reference range — with increased cardiovascular risk through direct myocardial and vascular effects, hypertension, and metabolic dysregulation.

Reference ranges

Standard reference

15–65 pg/mL (1.6–6.9 pmol/L) # REVIEWER FLAG: Confirm Boston Heart Diagnostics reference range for intact PTH — values vary between immunoassay platforms and generations. Second-generation intact PTH assays (measuring PTH 1-84 plus PTH 7-84 fragments) and third-generation whole/bio-intact PTH assays (measuring PTH 1-84 exclusively) produce different numerical results and have different reference intervals. Confirm which assay generation Boston Heart Diagnostics uses and whether the reference range is age-stratified — PTH rises modestly with age, particularly in postmenopausal women with vitamin D insufficiency.

Functional medicine optimal

15–40 pg/mL (functional medicine and preventive cardiology optimal — the lower half of the reference range is associated with better bone and cardiovascular metabolic outcomes when calcium and vitamin D status are adequate; PTH above 55 pg/mL in the context of vitamin D insufficiency represents a functionally secondary hyperparathyroid state even when technically within range). # REVIEWER FLAG: The 15–40 pg/mL functional optimal is used in integrative and preventive medicine but is not a standardised clinical guideline threshold — reviewer to confirm appropriate framing and whether the cardiovascular PTH-risk literature should be cited to support this range.

Units

pg/mL, pmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.