THE THYROIDAL UPTAKE OF STABLE IODINE COMPARED WITH THE SERUM CONCENTRATION OF PROTEIN-BOUND IODINE IN NORMAL SUBJECTS AND IN PATIENTS WITH THYROID DISEASE*†

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Abstract
THE uptake of radioactive iodine (I131) by the thyroid gland has beer shown, in general, to be in good agreement with the state of thyroid function (1). With gross alterations in the intake of stable iodine (I127) and in patients who have received treatment for thyroid disease, the usual relationship between radioiodine uptake and thyroid function may be altered. Of particular clinical importance are the high radioiodine uptakes which have been noted in patients who have received radioiodine or surgical treatment for rryperthyroidism and who, by clinical and other laboratory criteria, are euthyroid (2). Conversely, normal radioiodine uptakes have been observed in treated patients who are still hyperthyroid (3). These findings could be explained either by 1) a disturbance in the orderly secretion.of thyroid hormone of such a nature that iodine which is taken up by the gland is not released as circulating hormone, or 2) changes in the amount of stable iodine in extracellular fluid which is available for uptake by the thyroid gland, with the result that proportionately more or less of a dose of radioiodine is taken up by the thyroid gland than would ordinarily be the case at a given level of thyroid function. Our studies would support the latter hypothesis.