|Values are valid only on day of printing.|
Detection of pancreatic endocrine tumors
Assessment of vagal nerve function after meal or sham feeding
Pancreatic polypeptide (PP) is secreted by the pancreas in response to hypoglycemia, ingestion of food, or "sham" feeding (food is chewed, but not swallowed), secondary to vagal nerve stimulation. Secretion is blocked by vagotomy or atropine.
The exact physiologic role of PP is undetermined, although the hormone is thought to be involved in exocrine pancreatic secretion and gallbladder emptying.
Markedly elevated levels are often associated with endocrine tumors of the pancreas (eg, insulinoma, glucagonoma, PPoma: pancreatic polypeptide-secreting tumor of the pancreas) Patients with diabetes may also have elevated PP levels.
A lack of response to sham feeding may indicate vagal nerve damage (eg, surgery-related nerve damage, autonomic nerve disorders). Extensive pancreatic destruction (eg, chronic pancreatitis, pancreatic cancer) may also result in low basal PP levels and a lack of response to sham feeding.
0-19 years: not established
20-29 years: <228 pg/mL
30-39 years: <249 pg/mL
40-49 years: <270 pg/mL
50-59 years: <291 pg/mL
60-69 years: <312 pg/mL
70-79 years: <332 pg/mL
> or =80 years: not established
High levels may be seen in pancreatic endocrine tumors, diabetes, and a nonfasting state. Markedly elevated levels may be seen in some pancreatic exocrine tumors.
A normal response to a sham feeding consists of a rapid pancreatic polypeptide (PP) rise over baseline followed by a return to baseline. With vagal damage, no increase over baseline is seen.
Pancreatic polypeptide (PP) normal values increase with age (approximately 20 pg/mL per decade).
Nonfasting state results in falsely elevated values.
The sham feeding test is invalid if food is swallowed. Ingestion of food typically results in a significant and prolonged PP increase over baseline (typically >200 pg/mL).
This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. A recommended time period before collection cannot be made because it will depend on the isotope administered, the dose given and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held and assayed after the radioactivity has sufficiently decayed. This will result in a test delay.
1. Panzuto F, Severi C, Cannizzaro R, et al: Utility of combined use of plasma levels of chromogranin A and pancreatic polypeptide in the diagnosis of gastrointestinal and pancreatic endocrine tumors. J Endocrinol Invest. 2004 Jan;27(1):6-11
2. Brimnes Damholt M, Rasmussen BK, Hilsted L, et al: Basal serum pancreatic polypeptide is dependent on age and gender in an adult population. Scand J Clin Lab Invest 1997 Dec;57(8):695-702