TRIIODOTHYRONINE IN THE SERUM OF PATIENTS TREATED WITH RADIOACTIVE IODINE*†

Abstract

THE presence of triiodothyronine in the serum of man was first demonstrated by Gross and Pitt-Rivers (1). In a previous report we described various radioiodinated amino acids, including triiodothyronine, which appeared in the sera of patients treated with radioactive iodine (2). Because labeled triiodothyronine was present in some of the samples of serum taken twenty-four hours after the administration of the I¹³¹, the occurrence of iodinated compounds in the serum was explored further by the method of chromatographic fractionation. The following were investigated: 1) the frequency of occurrence of triiodothyronine in both Graves' disease and hyperfunctioning adenomatous goiter, 2) whether triiodothyronine is present in patients with normal functioning thyroid tissue, 3) the earliest time at which the compounds, especially triiodothyronine, are demonstrable in the serum, 4) whether radiation effect could explain the presence of the compounds by the time they first became detectable, and 5) the relationships between the circulating levels of thyroxine and triiodothyronine.