TEN YEARS' EXPERIENCE WITH RADIOACTIVE IODIDE*

Abstract

Radioactive iodide is an effective agent in the control of hyper-thyroidism caused by a diffusely hyperplastic thyroid. The biologic response to this form of radiation is gradual and patients may continue to respond over several mos. Myxedema has appeared years after the original cell injury. Following radiation therapy with I131, studies by means of thyroidal tracer uptakes of radioactive iodide, serum protein-bound I detns., and basal metabolic rates reveal several patterns. The patient may become myxedematous or euthyroid, or continue in persistent hyperthyroidism with the usual indices. However, dissociation of the indices of function was observed in 2 groups; 1st, in several apparently euthyroid patients with tracer uptakes under 20%, serum protein-bound I levels less than 3 [mu]g. per 100 ml., and basal metabolic rates above -20%; 2d, in those patients who are toxic with a high protein-bound I level and a high basal metabolic rate but with a normal thyroidal uptake of radioactive iodide. I131 radiation produces fibrosis and cellular damage in the thyroid resulting in bizarre nuclear forms; yet the follicles appear hyperplastic. Histologic sections from 44 thyroids studied after radiation revealed no evidence of malignancy.