Failure of exogenous secretin to induce secretion of calcitonin in man

The effect of secretin on calcitonin secretion from the human thyroid gland was studied in 15 patients undergoing thyroid and parathyroid surgery. Secretin was administered into the inferior thyroid artery at two different doses (0.75 and 7.5 CU) and into a peripheral vein at a dose of 75 CU. Blood samples for measurements of calcitonin and calcium were collected from thyroid or peripheral veins. However, neither intraarterially nor iv administered secretin was able to evoke any significant calcitonin response as measured in thyroid or peripheral venous blood. The calcium level was unaffected by secretin. The results demonstrate that secretin does not act as a calcitonin secretagogue in man.