PTH assay
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Overview Parathyroid hormone (PTH) released from parathyroid glands. Plasma calcium usually operates negative feedback system on PTH release. Multiple metabolic fragments of PTH in circulation are cleared by glomerular filtration. Only intact PTH molecule is active. Uses In combination Diagnosis of primary hyperparathyroidism Diagnosis of renal secondary hyperparathyroidism Diagnosis of hypercalcemia Diagnosis of primary hypoparathyroidism Source of test material Standard venipuncture Quantity of test material 1 ml EDTA plasma. Heparinized plasma or serum can be used (depending on laboratory used). Sample collection technique Collect sample and separate within 1-2 hours. Sample transport details should be obtained from individual laboratory. Quality control Timing of test Fast overnight. Biphasic circadian rhythm of PTH release so sample mid-morning at low point of secretion. Sample storage Must be chilled immediately following sample or frozen to -10 to -20°C after separation. Sample transport Overnight delivery on frozen gel packs. Package according to mailing regulations Methodologies Radioimmunoassay (RIA). Modern assay is a sensitive 2-site intact PTH assay:Measures functional parathyroid output. Less increase in PTH in renal failure (most increase is due to retention of inactive fragments). Normal (reference) values Normal range 2-13 pmol/l. Hypercalcemic dogs with non-parathyroidal disease should have low to low-normal basal PTH. Hypocalcemic dogs with non-parathyroidal disease should have high-normal to high basal PTH. Abnormal values Elevated or high normal PTH in hypercalcemic dog is suggestive of primary hyperparathyroidism Errors and Artifacts Extremely elevated basal PTH (5-100 pmol/l) levels can be seen in dogs with renal failure Low PTH in hypocalcemic dog is suggestive of primary hypoparathyroidism. Publications Refereed papers Recent references from PubMed . Torrance A G & Nachreiner R (1989) Human parathyroid assay for use in dog - validation, sample handling studies and parathyroid function testing. Am J Vet Res 50 , 1123-1127. Torrance A G & Nachreiner R (1989) Intact parathyroid assay and total calcium concentration in the diagnosis of disorders of calcium metabolism in dogs. JVIM 3 , 86-89. Vetstream contributor(s) Dr David Bruyette DVM DipACVIM , VCA West Los Angeles, 1818 South Sepulveda Boulevard, Los Angeles, CA 90025, USA.Dr Peter A Graham BVMS, PhD, CertVR, MRCVS, Section Chief, Veterinary Diagnostic Endocrinology, Animal Health Diagnostic Laboratory, Michigan State University, PO Box 30076, Lansing, MI 48909-7576, USA
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CANIS LAB00199
Assay should be interpreted in association with calcium 
or preferably ionized calcium.
Special sample handling required.