Identification and Estimation of Undegraded Thyroglobulin in Human Serum¹

Abstract

A radioimmunoassay for the detection of thyroglobulin in human serum having a sensitivity of 10 ng/ml is described showing that conventional techniques can be applied to the assay of large globular proteins. In 60% of normal sera the assay was positive. The serum of athyreotic cretins gave negative results. The active material exhibited the same behavior as native thyroglobulin when assayed at multiple dilutions and when subjected to ultracentrifugation and electrophoresis; furthermore, it could be absorbed out with insoluble preparations of rabbit or human antithyroglobulin antibodies. It was concluded that the assay was specific for thyroglobulin and that this protein is commonly present in an undegraded form in normal human serum. The implications of these findings are discussed in relation to theories of auto-immunity. (Endocrinology81: 421, 1967)