Assays / Hormones / Calcitonin (plasma)

Clinical Use
Diagnosis and management of patients with medullary cell carcinoma of the thyroid and screening family members.

After treatment, serial measurements permit assessment of therapeutic response and can be used to assess prognosis and to detect recurrence. Raised calcitonin concentrations have been found in patients with various non-thyroidal tumours. Calcitonin measurements in these circumstances are of no value.

Patient Preparation
After an overnight fast, take blood (5 mL) into a syringe and then transfer into a lithium heparin tube or green top vacutainer.

Measurement of the plasma concentration of calcitonin after fasting is usually sufficient for the diagnosis of medullary cell thyroid carcinoma. However, in some patients with this tumour, basal calcitonin concentrations are not always different from those of normal subjects. Provocative tests of calcitonin secretion may be necessary to establish the diagnosis. These tests include:

Pentagastrin test:

With the fasted patient recumbent throughout the test, take blood (5 mL). Inject pentagastrin solution (0.5 mg/kg body weight in 2 mL normal saline) intravenously within 10 - 15 sec Take further blood samples (5 mL) 2, 5, 10 and 15 min later.

Short calcium infusion test:

With the fasted patient recumbent throughout the test, take blood (5 mL). Slowly infuse calcium gluconate (2.5 mg calcium/kg body weight, 10% solution in saline, 10 - 15 mL) intravenously within 30-60 sec. Take further blood samples (5 mL) 2, 5, and 10 min later.

Combined pentagastrin and calcium infusion test:

With the fasted patient recumbent throughout the test, take blood (5 mL). Infuse intravenously within 30 sec a mixture of pentagastrin solution (0.5 mg/kg body weight in 2 mL normal saline) and calcium gluconate (2.5 mg calcium/kg body weight). Take further blood samples 2, 5, 10 and 15 min later.

Whisky test:

Take blood (5 mL). Give whisky (50 mL) orally (adults only). Take further blood samples 2, 5, 10, 15 and 30 min after ingestion.

Sample Preparation
If using vacutainers place on ice or transfer each sample promptly to a plastic heparin tube cooled in ice. Within 10 min, separate the plasma at 40C in a refrigerated centrifuge. Transfer to 2 plastic tubes (preferably 12 x 50 mm) and store at -20C. Visible haemolysis invalidates the results. Send one portion (1 mL) of each plasma to the SAS laboratory (advise before despatch). Ensure the samples remain frozen during transport. Retain the remaining portions frozen in reserve.

Reference Range
Please contact the appropriate SAS laboratory.

Centre offering this assay
Newcastle.

References
Dymling JF, Ljungberg O, Hillyard CJ, Greenberg PB, Evans IMA, MacIntyre I. Whisky: a new provocative test for calcitonin secretion. Acta Endocrinol 1976; 82: 500-509.

Graham SM, Genel M, Touloukian RJ, Barwick KW, Gertner JM, Torony C. Provocative testing for occult medullary carcinoma of the thyroid: findings in seven children with multiple endocrine neoplasia

Type IIa. J Pediatr Surg 1987; 22 (6): 501-503.

Wells SA, Jr, Baylin SB, Linehan WM, Farrell RE, Cox EB, Cooper CW. Provocative agents and the diagnosis of medullary carcinoma of the thyroid gland. Ann Surg 1978; 188 (2): 139-141

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