Meal-stimulated and atropine-inhibited secretion of pancreatic polypeptide in healthy subjects, members of MEA I families and patients with malignant endocrine tumours of the gastrointestinal tract.

Pancreatic polypeptide has been suggested as a marker for endocrine malignancies of the gastrointestinal tract. However, the secretion of PP shows great intra- and inter-individual variation, causing both false negative and positive results. In order to reduce these risks, we have evaluated a new combined stimulatory and inhibitory test of PP secretion. Six healthy subjects, 23 members of three MEA I families, seven patients with malignant pancreatic endocrine tumours and four patients with carcinoid tumours of the gastrointestinal tract were subjected to a standardized test meal, followed by intravenous atropine 60 min after the start of the meal. Serum PP was monitored during 2 h. In healthy subjects the meal caused a rapid increase in serum PP within 20 min and intravenous atropine caused a significant (P less than 0.05) decrease of serum PP within 15 min. Patients with malignant endocrine pancreatic tumours or carcinoids had a delayed response after the test meal, with maximum levels at 45 min, but still with a significant inhibition by atropine. Even tumour patients with initially normal or slightly increased basal PP levels showed this secretion pattern. Healthy members of MEA I families displayed identical PP curves to healthy subjects, whereas members with elevated basal PP levels who had been previously affected by hyperparathyroidism and/or prolactinomas showed similar secretion patterns to pancreatic tumour patients. We think that a meal stimulatory test is of great value in the diagnosis of gastrointestinal endocrine tumours and also in the identification of subjects with the MEA I trait, who are at high risk of having pancreatic endocrine tumours.