Unit Code 8014:
Pancreatic Polypeptide, Plasma
Useful For
Detection of pancreatic endocrine tumors
Assessment of vagal nerve function after meal or sham feeding
Clinical Information
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 (e.g. insulinoma, glucagonoma, PPoma). Patients with
diabetes may also have elevated PP levels.
A lack of response to sham feeding may indicate vagal nerve damage
(e.g. surgery-related nerve damage, autonomic nerve disorders).
Extensive pancreatic destruction (e.g. chronic pancreatitis, pancreatic
cancer) may also result in low basal PP levels and a lack of response
to sham feeding.
Reference Values
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
Interpretation
High levels may be seen in pancreatic endocrine tumors, diabetes,
and nonfasting state. Markedly elevated levels may be seen in some
pancreatic exocrine tumors.
A normal response to a sham feeding consists of a rapid PP rise over
baseline followed by a return to baseline. With vagal damage, no
increase over baseline is seen.
Cautions
Pancreatic polypeptide 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 samples received in the laboratory will be held and
assayed after the radioactivity has sufficiently decayed. This will result
in a test delay.
Clinical Reference
1. Schwartz TW: Pancreatic polypeptide: a hormone under vagal
control. Gastroenterology 1983;85:1411-1425
2. Koch MB, Go VL, DiMagno EP: Can plasma human pancreatic
polypeptide be used to detect disease of the exocrine pancreas?
Mayo Clin Proc 1985;60:259-265
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