Routine clinical application of an electrophoretic method for characterizing thyroid function

Plasmas of euthyroid, hypothyroid, and hyperthyroid patients were enriched with radiothyroxine, and electrophoresis was performed on cellulose acetate strips in both barbital and Tris maleate buffers, pH 8.6. Radiothyroxine partition among carrier plasma proteins was determined, and results were expressed as per cent total radioactivity bound to thyroid-binding globulin (TBG). The results obtained indicate that electrophoretic characterisation of thyroid function was best achieved by the utilization of data obtained from both buffers in that separation of hyperthyroid from euthyroid sera was successfully achieved only in barbital buffer, while the delineation of hypothyroidism was more precise in Tris maleate buffer. This technique represents a simple modification of a previously published method. The use of cellulose acetate rather than Whatman paper as the supporting medium for the electrophoretic procedure and the measurement of radioactivity by the automatic gamma well counter instead of strip-scanning greatly increases the facility and speed of the test while reproducing the consistency and diagnostic accuracy of the more elaborate procedure. The use of two buffer systems permits adequate delineation of the three levels of thyroid function and lends itself well to routine diagnostic studies. Further, since exposure of patients to exogenous iodine does not invalidate the procedure, it is a particularly useful additional parameter in the evaluation of thyroid function.