The changing pattern of circulating iodinated amino acids in a case of thyrotoxicosis

Abstract A case study is presented of a patient with thyrotoxicosis whose major circulating iodinated amino acid was T 3 , presumably as the result of an enzymatic defect of thyroidal hormone synthesis. Treatment with triiodothyronine was associated with partial clinical remission. Neither the protein-bound iodine nor the thyroidal uptake of I 131 was altered by treatment but the radiochromatograms indicated that the pattern of the circulating iodinated amino acids reverted to that usually found in patients with thyrotoxicosis.