Nature of the Inhibition by Thiocyanate of the Iodide Concentrating Mechanism of the Thyroid Gland

¹ From the National Cancer Institute, National Institutes of Health, Bethesda, Maryland

The dependence of the ratio of the radioiodide concentrations in thyroid gland and serum (T/S) on the serum iodide concentration for fixed serum thiocyanate concentrations was investigated in C₃H mice. The empirical equation (See PDF for Equation) where [SCN^–] and [I^–] are the serum thiocyanate and iodide concentrations in mg %, fitted the data within the limits of experimental error. Interpretation of the empirical equation was based on simple adsorption and active transport models of the iodide concentrating mechanism. The inhibition by thiocyanate of the thyroidal iodide concentrating mechanism appears to be competitive.