SERUM CONCENTRATION AND THYROIDAL UPTAKE RATE OF STABLE IODIDE IN VARIOUS STATES OF THYROID FUNCTION*

Abstract

The thyroidal uptake rate of stable iodide is equal to the product of the thyroidal clearance rate of iodide and the serum concentration of stable iodide. A new method is reported for the determination of serum iodide concentration from the specific activity of saliva iodine. The determined values of serum iodide concentration are smaller than those reported by others, but there was no significant difference in a series of 16 patients with various states of thyroid function. Daily hormone formation and release may be calculated from the thyroidal uptake rate of stable iodide. By comparison of the quantitative results of iodide metabolism with the clinical state, evaluation of effective thyroid function may be possible under various clinical or experimental conditions. The thyroidal radioiodide accumulation rate is a function of the thyroidal clearance rate of iodide, i.e., the capacity of the total gland to accumulate iodide. However, neither of these rates reflects the actual uptake rate of stable iodide in every case, owing to varying serum iodide concentration.