RESIN UPTAKE OF RADIOTHYROXINE FROM SERUM IN THYROID DISEASE AND IN PREGNANCY*†

Abstract

Further studies on the in vitro resin uptake of thyroxine-I131 from serum in thyroid disease and in pregnancy are described. Aliquots of serum containing thyroxine-I131 were equilibrated in test tubes with 1.0-ml. volumes of the anion exchange resin, Amberlite IRA-400, prepared with tris-maleate buffer, pH 5.2. The fraction of radioactivity remaining on the resin, expressed as a percentage of the normal control value, was significantly higher in hyperthyroidism and lower in pregnancy and in hypothyroidism than in the normal control subjects. These data suggest that the resin procedure provides an in vitro method for evaluating thyroid function and distinguishing between the nonpregnant and the pregnant state.