The "low TBG syndrome" in patients on chronic hemodialysis: evolution after renal transplantation

Patients on chronic hemodialysis may have a spuriously low TBG level, tentatively ascribed to uremia-induced changes in TBG immunoreactivity. In order to test this hypothesis, the effect of restoration of a normal renal function on TBG immunoreactivity was evaluated. TBG concentration was measured in 20 patients both by radioimmunoassay and by a T4-binding capacity assay, before, 4 and 10 months after a successful renal transplantation. Mean pretransplant TBG value measured by RIA was in the low normal range (1.60 +/- 0.14 mg/dl; normal limits 1.6-2.4 mg/dl). Twelve patients (60%) had TBG levels below 1.6 mg/dl (group I), while T4-binding capacity of TBG (TBC) measured in 7 of them was normal, so that the TBG/TBC ratio was characteristically reduced. The 8 remaining patients (group II) had TBG levels within or slightly above the normal range (mean value 2.26 +/- 0.17 mg/dl) and in the 5 tested patients, TBC and TBG/TBC ratio were normal. Four months after transplantation, mean TBG increased significantly in group I from 1.15 +/- 0.03 mg/dl before transplantation to 1.54 +/- 0.12 mg/dl (p less than 0.01). TBC increased also from 269 +/- 37.5 to 335 +/- 24 nmol/l (p less than 0.01) but to a significantly lesser extent than TBG (24% vs 48%, p less than 0.05). As a result, the TBG/TBC ratio returned to normal values, rising from 0.79 +/- 0.07 to 0.95 +/- 0.07 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)