Effect of meal on serum parathyroid hormone and calcitonin: possible role of secretin.

Purified secretin infused in an estimated physiological dose caused an increase in serum immunoreactive PTH (iPTH) and calcitonin (iCT) in man. Ingestion of a gastric acid-stimulating test meal, a procedure known to increase endogenous secretin, caused increases in serum iPTH and plasma iCT in normal subjects. Ingestion of antacid with the test meal blunted the increase in both iPTH and iCT. Ingestion of the test meal by pernicious anemia patients with achlorhydria caused no stimulation of either serum iPTH or plasma iCT. Therefore, based on the observations that 1) exogenous secretin stimulated iPTH and iCT, 2) an acid-stimulating test meal is known to stimulate endogenous secretin release (4), 3) the test meal increased both serum iPTH and iCT in normal man, an effect nullified by simultaneous antacid ingestion, and 4) the test meal caused no increase in either iPTH or iCT in achlorhydric patients, we conclude that endogenous secretin possibly mediates this effect of test meal and, therefore, may play a physiological role in modulating the secretion of PTH and CT.