Inhibition of organic binding of iodine with graded doses of iodine in euthyroid men.

Abstract

ABSTRACT The inhibition of thyroidal organic binding of iodine by iodide (Wolff-Chaikoff effect) was studied in 15 euthyroid men. The subjects received 5 U thyrotropin im for 3 consecutive days and varying doses of iodide for 48 hr before measuring the thyroid uptake of 132I. After the determination of the 3 hr thyroid 132I uptake, serum iodide, and thyroid iodide uptake, 1 g potassium perchlorate was given orally and thyroid 132I was measured 1 hr later. A positive response indicative of inhibition of organic binding was defined as a loss of 15% 132I in the thyroid at 3 hr. The base line thyroid uptake (5.00 ± 0.96%) and thyroid iodide uptake (4.48 ± 0.53 μg/hr) increased 3-fold with the administration of thyrotropin. As iodide intake increased, the serum iodide increased, the thyroid 132I uptake fell, but the thyroid iodide uptake increased progressively. A positive perchlorate response occurred in 11 subjects at iodide doses ranging from 1 to 16 mg daily, serum iodide concentrations of 2.5 to 36.9 μg/1...