A sensitive, convenient radioimmunoassay procedure which demonstrates that serum hTSH is suppressed below the normal range in thyrotoxic patients.

A highly sensitive radioimmunoassay procedures for the measurement of serum hTSH is described which permits delineation of the entire range of values in normal subjects (0.5-4.5 microU/ml). The procedure involves the concentration of hTSH from serum by adsorption to concanavalin A covalently bound to 4B Sepharose, Lactoperoxidase iodination of hTSH, and disequilibrium assay conditions. This method utilizes commonly available radioimmunoassay materials and is convenient to perform. Our results with this assay show that patients with thyrotoxicosis of a variety of etiologies have serum hTSH levels suppressed well below the normal range.