A new serum iodine component in patients with functional carcinoma of the thyroid.

Abstract

CERTAIN carcinomas of the thyroid in man acquire the function of normal thyroid tissue with respect to iodine metabolism (1, 2). Such tumors have the ability to concentrate iodide, convert it to organic form, and secrete organically bound iodine into the blood. They respond to thyrotropic hormone and to goitrogenic drugs with an increased avidity for iodide and, in the absence of normal thyroid tissue, may maintain their hosts in a euthyroid state. Observations on the chemical nature of the iodinated compounds elaborated by these tumors have, however, been scanty. The present report concerns studies on serum radioiodine in 23 patients with functional carcinoma of the thyroid, following 13 tracer doses and 37 therapeutic doses of I131. Thyroxine, and small amounts of triiodothyronine, constitute essentially all of the circulating iodine in normal and hyperthyroid individuals (3–6). These compounds have also been demonstrated in serum from patients with functional carcinoma of the thyorid, even in the absence of normal thyroid tissue (7–9). Thyroglobulin which has been discharged into the blood from intensively irradiated thyroid carcinoma likewise resembles normal thyroglobulin (8–11). Investigations employing zone electrophoresis have revealed a specific thyroxine-binding protein in serum from patients with thyroid carcinoma, which is similar to that in normal or hyperthyroid subjects (11–16). In the present study, however, a new serum iodine component has been found. The characteristics of this abnormality will be described, and its nature discussed.