The thyroidal uptake of radioactive iodine as modified by an iodine-restricted diet.

Abstract

ALOW thyroidal uptake of radioactive iodine (I131), in the absence of clinical hypothyroidism is not uncommonly noted. Low uptakes can frequently be related to exogenous thyroid medication, to recently administered antithyroid drugs, or to recently administered I127 in the form of medication or in contrast x-ray media. Patients with thyroid disorders often receive one of the foregoing substances, and the inquiring physician will look for a history of such medication when confronted with an unexpectedly low thyroidal uptake of I131. A high uptake of I131, on the other hand, is much less frequently encountered in the absence of hyperthyroidism, but the reasons for a high uptake may be much more obscure. Thus, without critical clinical and laboratory evaluation, a high uptake of I131 may lead to an erroneous diagnosis. High uptakes in the absence of hyperthyroidism have been noted by various investigators. Stanbury et al. (1) found abnormally high uptakes of I131 in goitrous individuals in the endemic goiter...