THE USE OF TRACER DOSES OF RADIOACTIVE IODINE, I131, IN THE STUDY OF NORMAL AND DISORDERED THYROID FUNCTION IN MAN*†

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Abstract
The uptake of a tracer dose of I131 by the thyroid gland has been measured by means of a Geiger counter, directly over and 15 cm. away from the gland, in normal subjects and in patients in whom a knowledge of thyroid function might be of interest. The normal range of uptake is between 10% and 35-40% of the admd. dose, at 24 hrs. There is a small but significant overlap of uptake between the control subjects and patients with toxic goiter. In cases of toxic goiter, the general correlation which exists between I uptake by the thyroid gland, and hormone secretion as reflected by the basal metabolic rate, can be disrupted by the treatment of the thyrotoxicosis. Lack of correlation between I uptake and basal metabolism may be found in active thyroiditis, malignant exophthalmos, Simmonds'' disease, Addison''s disease and anorexia nervosa. The depression of I uptake by previously admd. thyroid substance or stable I may persist for weeks.