THE BEHAVIOR OF LABELED THYROGLOBULIN AND LABELED THYROXINE IN PATIENTS WITH MYXEDEMA

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Abstract
Comparative studies with labeled inorganic iodide in 2 myxedematous patients were made during hypothyroid and euthyroid states. During myxedema, there was localization of radioiodide only in residual thyroid tissue. At a normal metabolic level, no thyroidal accumulation occurred. A small proportion of the labeled iodide appeared in the precip-itable fraction of serum during myxedema but not during euthyroidism. All of the I131 eliminated in the urine appeared in the form of iodide. 2-4% of the dose was excreted in the feces, all of it being "organically bound. Comparative studies were made with labeled thyroglobulin during hypothyroidism and euthyroidism in a patient with spontaneous myxedema. Temporary localization of radio-activity occurred over the liver. Within an hour I131 appeared in the serum in both precipitable and non-precipitable form. 58% of the I131 appeared in the urine, of which 90-95% was in the form of iodide. The remaining urinary I131 (5-10%) behaved like diiodotyrosine. About 11% of the dose was eliminated in the feces, all of it in precipitable form. Similar comparative studies with labeled racemic thyroxine disclosed considerable amts. of radioactivity over the region of the liver. Radioactivity in serum was initially entirely in precipitable form, after which inorganic iodide appeared. The urinary excretion was 28-48% of the dose and for at least 2 days after ingestion the curve of urinary excretion was linear in nature. 15% of the urinary I131 behaved as diiodotyrosine, and 85% behaved as inorganic iodide. 23-38% of the dose was found in the feces, the radioactivity being confined exclusively to the precipitable fraction.

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