Calcium-Pentagastrin Stimulation
Rationale: Calcium and pentagastrin stimulate the secretion of calcitonin by the parafollicular cells of the thyroid gland.1 This secretion is increased in patients with medullary thyroid carcinoma (MTC) relative to healthy individuals. Stimulation with the combination of calcium and pentagastrin produces better sensitivity and specificity for the diagnosis of MTC than basal calcitonin measurement or use of calcium or pentagastrin alone. The reference intervals in pg/mL established at baseline and after calcium/pentagastrin stimulation have been established by the assay manufacturer (Nichols Institute Diagnostics):
|
Baseline |
1 Minute |
2 Minutes |
5 Minutes |
10 Minutes |
|
|---|---|---|---|---|---|
|
Adult female (n=30) |
<4.6 |
<41 |
<70 |
<39 |
<23 |
|
Adult male (n=30) |
<11.5 |
<342 |
10−491 |
8−343 |
<112 |
Protocol: The patient should fast overnight prior to the stimulation procedure. The patient should remain supine during the procedure. A baseline serum sample should be collected for calcitonin measurement. Calcium (2 mg/kg) should be administered intravenously over 60 seconds followed by pentagastrin (0.5 μg/kg) over five seconds. Samples should then be collected for calcitonin at 1, 2, 5, and 10 minutes.
Orderable Test: Calcitonin (Thyrocalcitonin), Serum, Five Specimens (026807) (Baseline, 1-, 2-, 5- and 10-minute)
References
1. Endres DB, Rude RK. Mineral and bone metabolism. In: Burtis CA, Ashwood ER, eds.Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders; 1999:1395-1457.