THE URINARY EXCRETION OF RADIOACTIVE IODINE AS AN AID IN THE DIAGNOSIS OF HYPERTHYROIDISM

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Abstract
The urinary excretion of tracer doses of radioactive iodine by thyrotoxic patients, by non-thyrotoxic patients initially suspected of having Graves'' disease, and by non-thyrotoxic patients given iodine for some other research purpose, was studied in an attempt to determine its clinical usefulness in establishing the diagnosis of hyperthyroidism. The mean excretion by 22 thyrotoxic patients was 25% (range, 7-45%) and by 30 non-thyrotoxic patients 60% (range, 23-98%). There was considerable overlapping between thyrotoxic and non-thyrotoxic patients in the range 20-40%. However, the finding of a low urinary excretion of iodine aided in establishing the diagnosis in certain clinically equivocal cases. The finding of a high urinary excretion of iodine was of aid in excluding hyperthyroidism in some borderline cases in whom a truly basal metabolic rate could not be obtained. Specifically, the exclusion of Graves'' disease was facilitated in patients exhibiting hyperme-tabolism due to alcoholism, anxiety, compensated hypertensive cardiovascular disease, Parkinsonism, pheochromocytoma and thyrotoxicosis factitia.