I131METABOLISM IN THYROID SLICES OF PATIENTS WITH VARIOUS THYROIDAL DISORDERS*

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Abstract
Slices of thyroid tissue, obtained at operation from euthyroid patients and from patients with Graves'' disease, adenoma, carcinoma and several types of thyroiditis were studied in a gravity-flow system of incubation in a medium of constant composition containing I131. The metabolism of I131 was expressed in terms of the clearance of I131 by the slice, tissue-medium (T/M) gradients, ability to bind iodine in organic form, and ability to discharge accumulated radioiodine in response to thiocyanate both in the unblocked state and after blocking with methimazole. Slices of normal thyroid tissue had similar clearance values (0.03 ml/min./Gm.) and T/M ratios (3 to 4) whether organic binding was permitted or abolished. Only half of the accumulated Il31 was protein-bound when binding was allowed, and the remaining I131 was dischargeable by thiocyanate. When Lugol''s solution had been administered preoperatively, the above values were reduced to 50 and 75 per cent. The clearance by slices of exophthalmic goiters was tenfold, and the T/M ratios sixfold greater than those of normal tissue. The protein binding was one third that of normal tissue. Thiocyanate induced marked discharge of I131 from either the blocked or the unblocked slice. The suppression due to preoperative administration of Lugol''s solution was proportionally the same as noted for normal slices, but the suppressed exophthalmic-goiter tissue still metabolized I131 in amounts five to eight times greater than did the suppressed normal tissue. Adenomatous tissue generally metabolized I131 in the same manner as normal thyroid tissue. However, in 5 cases, thiocyanate did not discharge I131 from the unblocked slice, and in 3 cases thiocyanate was ineffective in both the blocked and the unblocked slice. Three of the 4 thyroid carcinomas metabolized I131 in the same manner as normal tissue; in the fourth, however, the accumulation of I131 followed the pattern observed in Graves disease, though less intense. Thiocyanate did not discharge I131 from slices of the first 3 carcinomas, but did so readily from the fourth or hyperfunctioning" tissue. Slices from cases of Hashimoto''s thyroiditis were hyperfunctional with respect to I131 metabolism, but less so than slices from cases of Graves'' disease. Thiocyanate induced substantial losses of I131 from either blocked or unblocked tissue. Tissue from 2 cases of granulomatous thyroiditis showed values for I131 metabolism like those of normal tissue, except for the extremely low content of protein-bound I131.