A RADIOIMMUNOASSAY OF THYROXINE

Abstract

A simple, sensitive, specific and precise radioimmunoassay (RIA) for measurement of serum thyroxine (T4) is described. The RIA employs rabbit anti-thyroglobulin antiserum as the T4-binding protein. The precision, reproducibility and practicality of the RIA are comparable to those of competitive protein binding assay (CPBA) using serum TBG as the T4-binding protein. However, the higher sensitivity and thereby a more extended standard curve of the RIA allows measurements of T4 in a larger range (1.2 to 40.0 ug per 100 ml) using 1/4 the sample volume required for the CPBA. The RIA appears particularly useful for measuring T4. in serum of infants and small experir mental animals where sample availability may be limited.