Gel filtration profile of circulating immunoreactive thyrotropin and subunits of myxedematous sera.

Five sera from hypothyroid patients were passed through gel-filtration columns and the collected fractions were analyzed in three different radioimmunoassays (hTSH-anti-hTSH; hTSHbeta-anti-pTSH; hLH-alpha-anti hLHalpha). For each immunological system, cross reactions were carefully studied. In the hTSH system one main peak was observed at the elution position of the entire molecule, with variable contributions in the subunits area. In the alpha subunit system, every profile showed an asymmetric peak, corresponding roughly to the position of the entire molecule; only two sera exhibited small amounts of free alpha chain. In the beta subunit system, a high molecular weight (100,000 or more) immunoreactive protein was present in every serum. Moreover, cross-reacting intact molecule was eluted as a second peak and in four sera free beta chain was detected. The significance of the big beta subunit, detectable only in the beta assay, is not elucidated.