Radioimmunoassay curve for T4 with anti-T4 antibodies

If endogenous human anti-T4 antibodies are present and bind radiolabeled T4 (*T4) then the amount of *T4 that binds to rabbit anti-T4 antibody and then is precipitated by goat anti-rabbit gamma globulin is reduced. Low percent *T4 binding correlates with high serum concentrations of T4, giving a spuriously high result.