Are elevated pancreatic polypeptide levels in patients with insulinoma secondary to hypoglycaemia?

In 13 patients with insulinoma, human pancreatic polypeptide (hPP) was measured under basal conditions, after a mixed meal, and during a fast of up to 72 h. Significant negative correlatons between hPP and plasma-glucose levels were found both under basal conditions and during fasting. Patients with insulinoma and basal plasma-glucose values above 60 mg/dl had hPP values similar to those in control subjects, whereas insulinoma patients with plasma-glucose values under 60 mg/dl had significantly higher hPP values (323 versus 115 pg/ml). The mean hPP response to a mixed meal was similar in patients with insulinoma and in control subjects. hPP values during symptomatic hypoglycaemia were higher in insulinoma patients than controls fasted for comparable times (751 versus 171 pg/ml). Under conditions of euglycaemia, hPP is not a reliable marker for insulinoma.