THE METABOLIC FATE OF I131AFTER LARGE THERAPEUTIC DOSES IN PATIENTS WITH METASTATIC CARCINOMA OF THE THYROID*†

Abstract

The metabolic fate of large therapeutic doses of I131 in 8 patients with metastatic carcinoma of the thyroid was observed. After initial periods of adjustment the radiation measured from the body as a whole followed a simple exponential decay, with biological half periods which varied from 3-12 days. There is a rapid fall in the urinary excretion rate of I131 for the first day or two and in some patients this was followed by a secondary rise. The rapid fall in the iodide phase of the blood curve was superceded by a secondary rise and an adjustment to a simple exponential decay rate, which had a biological half-period appreciably longer than that of the urine.