Effect of exogenous secretin on calcium and parathormone levels in man

Gastrointestinal hormones containing the C-terminal tetrapeptide of gastrin are involved in calcium homeostasis. The aim of this study was to investigate: 1) the effect of a standard meal (schedule a) and of a duodenal infusion of 5% aminoacid solution (schedule b) on calcium, CT and PTH serum levels in man; 2) the behaviour of these parameters during I.V. infusions of pentagastrin (mcg 1.5/Kg-hour), sincalide (mcg 0.04/Kg-hour) and caerulein (ng 75/Kg-hour) (schedule c). In order to avoid any possible interference by endogenous secretin release, schedule c was performed in 5 patients previously submitted to total gastrectomy. Schedule a and b were studied in 5 healthy volunteers. After a standard meal a slight increase of CT and PTH was measured. Duodenal infusion of aminoacid was followed by hypocalcaemia and slight but constant rise of CT levels, without significant variations of circulating PTH. Pentagastrin, sincalide and caerulein induced a slight but significant hypocalcaemia and a rise of serum CT levels, together with a significant increase of serum PTH. These findings suggest that peptides containing the C-terminal tetrapeptide of gastrin directly affect calcium homeostasis in the absence of secretin release.