Effect of Increased Dietary Iodide on Thyroid Accumulation and Secretion in Euthyroid Arkansas Subjects

Publisher Website
Google Scholar
Abstract
Thyroid function was investigated in 20 euthyroid Arkansas subjects during administration of daily iodide supplements of 0, 252 and 1009 [mu]g I/day; a period of 13 weeks was allowed for equilibration at each higher dose level. Chemical assays and I131 counting methods were used to measure thyroidal and renal clearance rates, thyroidal accumulation of I127 and daily thyroxine turnover. The computed mean plasma iodide levels, [sigma] , ranged between 0.008 and 0.03 [mu]g/ml. With increasing iodide intake there occurred a significant decrease in thyroidal radioiodine clearance rate k1 and an increased thyroidal I127 accumulation, whereas thyroxine turnover rate remained substantially constant. When these results are considered together with those from publications of other investigators, the following relation appears to be valid for the average euthyroid subject over a wide range of iodide intake 105 k1 =22.8+ 0.254/[sigma]. The presence of the constant term in this expression indicates that thyroidal iodidel27 accumulation, A, exceeds hormone turnover, H, by an amount that increases with increasing iodide intake; at low levels of iodide intake A and H would be nearly equal.