Meal-related changes in plasma calcitonin levels in patients with medullary thyroid carcinoma.

In 3 patients with medullary thyroid carcinoma, plasma calcitonin levels showed 3 distinct peaks associated with a simultaneous rise in plasma gastrin after each meal. It is suggested that endogenous gastrin secreted following food intake stimulated the calcitonin secretion from the tumor. The peak of the plasma calcitonin secretion after the evening meal was less prominent than that for breakfast or lunch, while no significant differences were observed in peak values in plasma gastrin after each meal. The reason for this discrepancy remains to be clarified.