PARATHYROID HORMONE (PTH) - (P)
Test Code: PTH
Test Indications: Parathyroid hormone (PTH) is formed in the parathyroid glands located at the posterior aspect of the thyroid gland and is secreted into the blood stream. PTH, together with vitamin D and calcitonin, mobilizes calcium and phosphate from the skeletal system and increases calcium uptake in the intestine and excretion of phosphate by the kidney. The interraction of PTH and calcitonin ensures blood calcium homeostasis. Parathyroid gland disorders lead to hypercalcemia or hypocalcemia due to a change in PTH secretion. The test is therefore useful in the differential diagnosis of hypercalcemia disorders, hypoparathyoidism and primary, secondary and tertiary hyperparathyroidism.
Recommendations: Simultaneous calcium measurement is required for appropriate interpretation.
Patient Preparation Instructions: Multivitamins (45–125 µg biotin) or biotin-only supplements up to 1 mg per day do not interfere with this test. Samples should not be taken from patients receiving therapy with high biotin doses (i.e. >5 mg/day) until at least 8 hours after the last dose.
This assay has 99% cross-reactivity to the biologically inactive carboxy-terminal PTH fragment 7-84. PTH fragments are primarily cleared by the kidney and accumulate in renal failure. Therefore, healthy population reference ranges do not apply in renal failure.
Stability 3 days refrigerated, 6 months frozen.
Plasma: 2.0 mL
Pediatric Plasma: 0.3 mL
Serum: 2.0 mL
Samples must be transferred to an aliquot tube and stored frozen if analysis will not be complete within 48 hours (#110-10-05 Serum / Plasma Separation Procedure & Transport)
17 - 60 ng/L
Reference values are based on healthy, normocalcemic, vitamin D-replete individuals with normal renal function