THYROXINE BINDING CAPACITY OF SERUM ALPHA GLOBULIN IN HYPOTHYROID, EUTHYROID, AND HYPERTHYROID SUBJECTS 1

Abstract

Thyroxine labeled with I131 was mixed with the sera of patients with varying thyroid function, and these mixtures were subjected to paper electrophoresis. The concentration of radio-thyroxine in the thyroxine binding globulin (TBG) was determined. The amount of added thyroxine bound by the TBG varies inversely with thyroid function. This is assumed to indicate that this protein is relatively saturated with endogenous thyroxine in the hyperthyroid and relatively unsaturated in the hypothyroid. From evidence in an athyreotic individual it appears that the total thyroxine binding capacity of the TBG is 0.4 [mu]g/ml, only 1/3 of which is utilized in the normal subject.