Effects of Secretin on Parathyroid Hormone and Calcium in Normal Subjects, Patients with Hyperparathyroidism and Patients with Gastrinoma

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Abstract
In vitro studies have demonstrated that secretin can stimulate the release of parathyroid hormone (PTH), but reports concerning its effects on PTH and Ca in vivo are contraditory. A bolus injection of secretin (75 IU) was given to 12 normal subjects and 10 patient with primary hyperparathyroidism (HPT) to examine this question. Six of the patients had multiple endocrine neoplasia and 5 had endocrine pancreatic tumors (EPT). Three normocalcemic patients with EPT were also included in the study. The mean serum gasrin level rose significantly (from 19 to 40 pmol/l, P < 0.01) within 15 min of secretin injection in the normal subjects. HPT patients without EPT had somewhat higher mean basal level of gastrin (39 pmol/l, P < 0.05 compared with controls), but it did not increase significantly after the secretin bolus. In 6 EPT patients the gastrin concentrations rose by > 300 pmol/l. Although secretin had a biological capacity to release gastrin, it had no discernible effects on either serum PTH or serum Ca in any of the groups studied. Nor were any changes in PTH or Ca observed when secretin was given as a continuous infusion (3 IU/kg per h) over 90 min. The data do not support the concept that secretin, in vivo, is a secretagogue of PTH.