RADIOIODINE EQUILIBRIUM STUDIES OF THYROID AND BLOOD

Abstract
A method of isotope equilibrium has been used to study iodinated amino acids of thyroid and blood in the rat. Iodide, monoiodotyrosine, diiodotyrosine, thyroxine and 3′,3,5-triiodothyronine were found to comprise 13%, 20%, 46%, 18%, and 3% of the thyroidal iodine respectively. Thyroxine accounted for approximately 80% of the blood iodine, triiodothyronine 3.5% and the iodinated tyrosines from zero to 4%. These figures are consistent with the hypothesis than in the rat, thyroxine and triiodothyronine contribute approximately half each of the total physiological activity of the thyroid hormones.