Update on pancreatic polypeptide as a specific marker for endocrine tumours of the pancreas and gut.

Serum levels of pancreatic polypeptide (PP) were determined in 31 patients with endocrine tumours, localized in the pancreas (n = 16), small intestine (n = 13) and respiratory tract (n = 2). Two further patients with laxative abuse were investigated. Elevated serum levels in the peripheral circulation were noted in 56% of the patients with pancreatic tumours, in 60% of those with gut or bronchial tumours and in both patients with laxative abuse. Our study suggests that the elevated PP concentrations found in connection with endocrine gastrointestinal tumours originate from non-tumour pancreatic PP cells and only occasionally from the tumour. PP is a valuable tumour marker for endocrine gastrointestinal tumours, although it is not specific for pancreatic tumours. Certain inflammatory diseases, renal function and consumption of laxatives must be considered when evaluating elevated PP levels. Serum PP seems to be of limited value for evaluating the response to cytotoxic therapy.