Evidence for a factor in the sera of patients with nonthyroidal disease which inhibits iodothyronine binding by solid matrices, serum proteins, and rat hepatocytes.

Abstract

We have measured the plasma protein binding of [125I]T4 and [125I]T3 in several groups of patients using assays of equilibrium dialysis and binding by dextran-coated charcoal carriedout under conditions of physiological pH. Subjects included 45 patients with nonthyroidalillnesses (NTI), 5 patients with hyperthyroidism, 5 with hypothyroidism, 1 with familial low T4-binding globulin (TBG), and 11 healthy controls. Both test results wereexpressed as the ratio of nonprotein-bound to protein-bound hormone, which was normalizedto the average ratio obtained for the control group [normalized dialysis ratio (NDR); normalized charcoal binding ratio (NBR)]. Our data suggest that for subjects with thyroid disease or alterations in TBG, both tests reflect similar changes in plasma protein binding and did not differ significantly from each other [low TBG; T4 NDR, 2.39; T4 NBR, 2.37; hyperthyroid: T4 NDR, 1.70 ± 0.29; T4 NBR, 1.53 ± 0.26; hypothyroid: T4 NDR, 1.10 ± 0.09; T4 NBR, 0.94 ± 0.11 (mean ± SD)]. Among NTI subj...