EFFECT OF IODINE ON THE THYROID GLAND IN GRAVES' DISEASE WHEN GIVEN IN CONJUNCTION WITH THIOURACIL—A TWO-ACTION THEORY OF IODINE 1

Abstract

The writers conclude that the involuting action of I observed in patients with Graves'' disease can be separated from the iodinating action of I. The data from which this conclusion was made were obtained from studies made on patients with Graves'' disease before treatment, after thiouracil had produced a fall in the BMR to normal, and after combined treatment with thiouracil and I. Micro -histometric studies were made of biopsy specimens taken before treatment and after thiouracil treatment but before any I was administered and on the operatively removed thyroids after combined thiouracil and iodine therapy. The urinary excretion of radioactive I before and during treatment with thiouracil was observed. The total and protein-bound I of the operatively removed thyroids after combined thiouracil and I treatment was detd. The mean thyroid acinar cell heights before any therapy averaged 12.9 micra, after thiouracil treatment 13.9 micra, and after combined thiouracil and I 7.2 micra. The urinary excretion of I before treatment averaged 25% of the administered tracer. During treatment with thiouracil, the avg. excretion was 80.3%. The avg. total thyroid I values after combined thiouracil and I treatment was 22.1 mg. % wet wt. The thyroid thyroglobulin I values averaged 7.0 mg. % wet wt. The latter values were similar to values obtained from the thyroids of thyrotoxic patients treated with thiouracil alone, i.e., avg. total thyroid iodine 18.8 mg. % and avg. thyroid thyroglobulin I 6.8 mg. %. Thus an involution of the thyroid cell occurred though the storage of I in the thyroglobulin fraction was inhibited. The authors hypothecate that the involuting action of I in Graves'' disease is accomplished through a block to the action of the thyrotrophic hormone on the thyroid cell.