THE METABOLISM OF IODOTYROSINES. IV. METABOLISM OF<i>l</i>-DIIODOTYROSINE IN PATIENTS WITH HYPOTHYROIDISM

Abstract

WHEN diiodotyrosine labeled with radioactive iodine is administered to normal subjects, almost all of the labeled iodine which appears in the urine is in the form of inorganic iodide. Albert and Keating (1), observing the disposal of labeled diiodotyrosine in 3 patients with treated myxedema, found that only approximately 5 per cent appeared in the urine as diiodotyrosine. The optical activity of the diiodotyrosine was not stated. Entirely comparable results have been obtained in 15 euthyroid patients with various diseases (2). When labeled racemic (dl) diiodotyrosine was injected intravenously into 3 patients with hypothyroidism and goiter, however, the labeled iodine which appeared in the urine was in the form of diiodotyrosine (3). No deiodination of diiodotyrosine could be demonstrated. Identical findings were obtained in 2 of these patients after they had been treated with desiccated thyroid. In the present study, the urinary disposal of levorotatory diiodotyrosine has been observed in a group of patients without thyroid disease and in patients with hypothyroidism and with clinical myxedema. The results are compared with those obtained from administration of racemic diiodotyrosine to euthyroid subjects.