BINDING OF THYROXINE BY SERUM PROTEINS EVALUATED BY EQUILIBRIUM DIALYSIS AND ELECTROPHORETIC TECHNIQUES. ALTERATIONS IN NON-THYROIDAL ILLNESS*

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Abstract
Binding of thyroxine by serum proteins of normal subjects, pregnant women, patients with hyperthyroidism and hypothyroidism, as well as patients with neoplastic and inflammatory diseases was studied by paper and starch-gel electrophoresis at pH 8.6 and equilibrium dialysis at pH 7.4. Levels of free thyroxine were elevated in hyperthyroidism, depressed in hypothyroidism, and normal in pregnancy. In patients with nonthyroidal disease, the binding of thyroxine by plasma protein was diminished and the concentration of free thyroxine elevated. Reduced binding of thyroxine was due to a marked fall in the concentration of thyroxine-binding prealbumin (TBPA) as demonstrated by a diminished protein stain of prealbumin 1 in starch-gel electrophoresis and a fall in the maximum binding capacity of TBPA on paper electrophoresis.