Metabolic clearance rate of radioiodinated human calcitonin in man.

The characteristics of the disappearance of radioiodinated synthetic human calcitonin from plasma have been studied in man. After single injection the disappearance curve was multiexponential. The number of exponentials of the theoretical curve fitting the best with the experimental data varied individually. Metabolic clearance rate was determined both from single injection and constant infusion studies, and fast initial distribution volume from the former. Metabolic clearance rate values in normal man calculated from constant infusion studies were 82.3 +/-3.4 ml/min per m(2). Values derived from single injection studies were similar, 77.0 +/-4.7 ml/min per m(2). These results were compared to those obtained in end stage, renal failure patients. Metabolic clearance rate was considerably lower and volume of fast initial distribution slightly larger in that group. This fact emphasizes the important role of kidneys in the utilization and/or the degradation of human calcitonin.