ABNORMAL RISE IN PANCREATIC-POLYPEPTIDE I N THE SECRETIN STIMULATION TEST - HYPOGLYCEMIA AS POSSIBLE CAUSE

Pancreatic polypeptide (PP) can he used as a marker for endocrine acti ve tumors originating from the pancreas. After intravenous administrat ion of secretin, individually divergent increases in plasma PP concent ration can be observed hampering interpretation of the stimulation tes t. Under certain circumstances elevated basal PP concentrations can be observed. Besides age, renal insufficiency and diabetes, hypoglycemia can cause high PP levels. We therefore enquired whether in patients w ith atypically high increase of PP after secretin this increase could be caused by hypoglycemia during the secretin stimulation test. In ord er to test this hypothesis we prospectively determined the plasma gluc ose and insulin concentrations in addition to the routinely measured g astrointestinal hormones in 19 patients referred for secretin provocat ion test. In the 16 patients in whom the increase of PP was not due to an endocrine active tumor or renal insufficiency, PP rose to 170+/-57 pmol/l (+/-SEM) 2 minutes after secretin administration. In parallel, plasma insulin concentration increased to 365+/-51 pmol/l 2 minutes a fter secretin. The maximal insulin concentrations correlated significa ntly with the PP concentrations observed at the same time (R = 0.73, p <0.01). The mean glucose concentration, however, remained constantly between 4.8+/-0.3 and 5.2+/-0.3 mmol/l and there was no correlation be tween the peak plasma PP concentrations after secretin and the plasma glucose concentrations (R = 0.07). The minimal glucose concentrations observed were 3.3 mmol/l in three patients (30 minutes after secretin in 2 patients and 45 minutes after secretin in one). The mean plasma g lucagon concentration rose to 22.5+/-4.1 pmol/l 10 minutes after secre tin. The secretin-induced increase in plasma PP concentration was para llel to the increase in plasma insulin and glucagon. However, hypoglyc emia as a possible cause of elevated PP levels did not occur in spite of the marked increase in insulin.