Thyroxine-binding prealbumin in thyrotoxicosis and hypothyroidism.

THYROXINE is reversibly bound in the plasma to three proteins: thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin. Changes in the binding capacities of TBG and TBPA in patients with thyroid disease have been reported previously (1, 2). Since starch-gel electrophoresis of serums of patients with thyrotoxicosis indicated a marked decrease in density of the stain in the zone of prealbumin, it was suggested that the diminished TBPA capacity in these patients was due to reduction of prealbumin concentration (1). However, no data are available indicating the actual concentration of these proteins in the serum. In the present study, the serum concentration of TBPA in patients with thyrotoxicosis and hypothyroidism has been determined quantitatively by an immunoehemical method.