Diagnosis of gastrinoma by the secretin suppression test

In contrast to normal physiologic feedback suppression of serum gastrin by secretin, a paradoxic rise in the serum gastrin level has been observed in patients with gastrinoma after the administration of exogenous secretin. Exploitation of this phenomenon in the differential diagnosis of gastrinoma has been restricted by limited individual experience. Serial serum specimens for gastrin radioimmunoassay were collected from 13 patients with histologically proved gastrinoma both before and after the administration of Boot's secretin, 3 units per kilogram. Thirty-nine others with histologically proved gastrinoma who had been studied with exogenous secretin were identified in the literature. Both the peak gastrin and the integrated gastrin responses were increased after secretin administration in each of the patients in this combined series, although the magnitude of the increase was small in four patients. The absence of physiologic suppression by secretin implies neoplastic autonomy of gastrin releasing sites. While an augmented gastrin response to secretin is commonly seen in patients with gastrinoma, from a physiologic standpoint, a lack of suppression constitutes a positive secretin suppression test. Accumulated experience is consistent and suggests that this test is an important adjunt in the differential diagnosis of hypergastrinemia.