THE ROLE OF GASTRIN AS A CALCITONIN SECRETAGOGUE

SUMMARY Our earlier observation that pentagastrin is a calcitonin (CT) secretagogue was confirmed and extended to include both synthetic human gastrin I and pure porcine gastrin II. The latter hormone was shown to stimulate the secretion rate of CT from thyroid preparations perfused in situ in anaesthetized pigs at concentrations (0·5 nmol/l) similar to those found after stimulation of gastrin production by a meat extract placed in the stomach (0·2 nmol/1). These concentrations of plasma gastrin are considerably less than those found in man in both pernicious anaemia and the Zollinger—Ellison syndrome, whereas the mean fasting plasma gastrin concentrations in normal human beings and pigs are similar. It is suggested that the comparatively high incidence of parathyroid hyperactivity in association with the Zollinger—Ellison syndrome may be a consequence of an increased CT secretion rate induced by hypergastrinaemia. Furthermore, the existence of a gastrointestinal—thyroid C cell system is proposed as an integral part of postprandial calcium homeostasis.