PTHrP may be used for the differential diagnosis of hypercalcaemia of unknown origin where other diagnostic tests have not identified the aetiology of the hypercalcaemia but where PTH and iCa suggest parathyroid independent hypercalcaemia. PTHrP is a hormone that can be produced by dogs, cats and horses with several different types of tumours and is considered to be the underlying cause of hypercalcaemia of malignancy in many but not all cases.

Almost all anal gland apocrine neoplasia, the majority of hypercalcaemic lymphomas and smaller percentages of myeloma and carcinomas are PTHrP positive. Circulating levels of PTHrP in normal dogs are almost undetectable (< 0.5 pmol/L). Levels greater than 2.0 pmol/L are considered significant in dogs. Cats appear to show similar values. Please note: SAMPLE PREPARATION IS CRITICAL FOR THE ACCURATE ANALYSIS OF PTHrP (see procedure for PTH on p53). THE APROTININ EDTA TUBE SUPPLIED WITH THE TRANSPORT PACK SHOULD BE USED FOR THE COLLECTION OF PTHrP SAMPLES.