FUNCTIONAL AND HISTOLOGIC EFFECTS OF THERAPEUTIC DOSES OF RADIOACTIVE IODINE ON THE THYROID OF MAN*

Abstract

Thyroid tissue was obtained from 29 patients by thyroidectomy, biopsy or autopsy, from 2 days to 8 yrs. after treatment with radioactive I. Anatomic changes, such as gross atrophy, telangiectases on the surface of the gland and adherence to adjacent structures were found in some thyroids. The chief microscopic changes attributable to this radiation were irregularity in size and outline of the nuclei and bizarre distortion of the chromatin patterns. Fibrosis associated with islands of acini, containing cells of variable height, seemed to be a characteristic reaction to radiation injury. Extrathyroidal tissue appeared to have escaped injury from radioactive I. Radioautographs of these thyroidal tissues disclosed that certain acini, although exhibiting bizarre nuclei, had a capacity to collect subsequent tracer doses of the isotope. Such areas of sublethal radiation injury probably are capable of producing thyroid hormone. In a series of over 400 patients treated with radioactive I at the Massachusetts General Hospital during the past 10 years no known carcinoma of the thyroid attributable to this agent has developed.