Pancreatic Polypeptide

Pancreatic polypeptide (PP) is a 36-amino-acid secretory peptide that is predominantly produced by the pancreas.¹ The exact physiologic role of PP in healthy individuals has not been fully defined.^1,2 It has been shown, however, that this peptide affects the secretion of pancreatic enzymes, water, and electrolytes.¹ Its effect is biphasic in that PP initially enhances secretion and then inhibits secretion.¹ PP increases gastric emptying and gut motility.¹ It also relaxes the pyloric and ileocecocolic sphincters, the colon, and gallbladder.¹ PP levels increase after ingestion of food and remain elevated from 4-8 hours.^1-3 Prolonged fasting, diabetes, and exercise can also increase PP levels.^2,3 Serum PP levels can be elevated in as many as 50% of patients with carcinoid syndrome.³ Increased levels can also be found in patients with duodenal ulcers and in patients with type I diabetes.¹ PP levels are often low in patients with pancreatic insufficiency or pancreatitis.¹

PP secretion can be increased by endocrine-active tumors of the pancreas.^2-5 Tumors that secrete only PP are rare with only 22 cases reported in the literature.^2,4 Seven of the reported cases developed a watery diarrhea hypokalemia achlorhydria (WDHA) syndrome, also referred to as Verner-Morrison syndrome, that is similar to that seen in VIPomas.² Another five reported cases had steatorrhea.² The last ten had silent or nonfunctioning tumors without hormone-related symptoms.²

Increased PP secretion has been frequently reported in patients with functioning and nonfunctioning pancreatic tumors that produce other endocrine peptides.^1-5 PP levels are often elevated in patients with VIPomas, glucagonomas, gastrinomas, and insulinomas.^1,2,5 Eriksson and colleagues found that PP levels were elevated in 74% of patients with endocrine pancreatic tumors and that this peptide serves as a good general marker for patients suspected of having pancreatic endocrine tumors.⁵

1. Henderson RA, Rinker AD. Gastric, pancreatic and intestinal function. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders Co;1999:1271-1327.

2. Pasieka JL, Hershfield N. Pancreatic polypeptide hyperplasia causing watery diarrhea syndrome: A case report. Can J Surg. 1999; 42(1):55-58 (review). PubMed 10071589

3. Vinik AI, Strodel WE, Eckhauser FE, Moattari AR, Lloyd R. Somatostatinomas, Ppomas, neurotensinomas. Semin Oncol. 1987 Sep; 14(3):263-281. PubMed 2820062

4. Bellows C, Haque S, Jaffe B. Pancreatic polypeptide islet cell tumor: Case report and review of the literature. J Gastrointest Surg. 1998 Nov-Dec; 2(6):526-532. PubMed 10457310

5. Eriksson B, Arnberg H, Lindgren PG, et al. Neuroendocrine pancreatic tumours: Clinical presentation, biochemical and histopathological findings in 84 patients. J Intern Med. 1990 Aug; 228(2):103-113. PubMed 2168468