Cholecystokinin (CCK)

Clinical Significance
Cholecystokinin is a 33 amino acid peptide having a very similar structure to Gastrin.  Cholecystokinin is present in several different sized forms including a 58 peptide Pro-CCK and 22, 12, and 8 peptide metabolites.  The octapeptide retains full activity of the 33 peptide molecule.  Cholecystokinin has an important physiological role in the regulation of pancreatic secretion, gall bladder contraction and intestinal motility.  Cholecystokinin levels are elevated by dietary fat especially in diabetics.  Elevated levels are seen in hepatic cirrhosis patients.  Cholecystokinin is found in high levels in the gut, in the brain and throughout the central nervous system.

Reference Range
Up to 80 pg/mL

CCK is measured by direct radioimmunoassay.

Patient Preparation
The patient should fast for 10 to 12 hours prior to collection of specimen. Antacid
medications and medications that affect intestinal motility should be discontinued, if
possible, for at least 48 hours prior to collection of specimen.

Specimen Collection
Collect 10mL blood in special ISI GI Preservative tube yielding special GI plasma and separate as soon as possible. Freeze plasma immediately after separation. Special GI
Preservative tubes are available from ISI. Minimum specimen size is 1 mL.

Important Precaution
CCK specimens must be collected using the GI Preservative tube. No other specimens
are acceptable.

Special Specimens
For tumor/tissue and various fluids (e.g., CSF, peritoneal fluid, synovial fluid), contact
ISI for requirements and special handling instructions.

Shipping Instructions
Specimens should be shipped frozen in dry ice.

1. Nakano I, Funakoshi A, Shinozaki H, et al. Plasma cholecystokinin and pancreatic polypeptide responses after ingestion of a liquid test meal rich in medium-chain fatty acids in patients with chronic pancreatitis. Am J Clin Nutr. Feb;49(2):247-51, 1989.
2. Chang T, Chey WY. Radioimmunoassay of cholecystokinin. Dig Dis Sci. May;28(5):456-68, 1983.
3. Rehfeld JF. Clinical endocrinology and metabolism. Cholecystokinin. Best Pract Res Clin Endocrinol Metab. 18(4):569-86, 2004.

CPT Code: 
Immunoassay  83519