Gastric secretion and hormonal interactions in multiple endocrine neoplasia type I.

Results of preparathyroidectomy and postparathyroidectomy studies in a patient with multiple endocrine neoplasia type I and gastrinoma suggest that hyperparathyroidism unmasks occult gastrinoma and related secretory abnormalities. Three of four diagnostic findings were later obscured by parathyroidectomy and normalization of serum calcium concentration. Basal acid output, basal acid output/maximal acid output ratio, and serum gastrin concentration were decreased from values consistent with gastrinoma to normal. The secretin stimulation test, though still positive, was attenuated. These observations suggest that in multiple endocrine neoplasia type I, normal values for serum gastrin concentration, gastric secretion, and secretin stimulation may not exclude gastrinoma. The investigations clarify the interpretation of a voluminous but confusing literature on the interrelationship between hyperparathyroidism and altered gastric function in the presence or absence of Zollinger-Ellison syndrome.