Iodine determined in purified thyrocalcitonin

Thyrocalcitonin has been suspected of containing iodine, because its analytical behavior and method of extraction are similar to that of iodinated peptides. The iodine content of increasingly pure thyrocalcitonin extracts was determined by two methods, Kolthoff's procedure and activation analysis, with good agreement. A possible link between calcium and iodine metabolism is suggested by these findings.