Serum thyroxine and thyroxine-binding proteins in chronic renal failure without nephrosis.

Total serum thyroxine (T4), free thyroxine index (FTI), thyroxine binding globulin (TBG) binding capacity, serum albumin, alpha-globulins and urinary protein excretion were measured in 50 patients with chronic renal failure, but without nephrotic syndrome. 25 patients were undergoing chronic hemodialysis. T4 was within the normal range in most patients. There was a tendency to lower T4 values as compared to an age and sex-matched control group, but this did not reach statistical significance. TBG was normal in most patients. 4 patients showed elevated TBG concomitant with elevation of other alpha-globulins. Serum albumin was significantly decreased. No correlation existed between daily protein excretion and TBG or alpha-globulins, but the correlation between serum albumin and proteinuria was highly significant. T4 and proteinuria correlated with borderline significance. A highly significant correlation between T4 and TBG-albumin values was found. No correlation existed between FTI and TBG-albumin levels. The data suggest that T4 and TBG are normal in most patients with renal failure, even in the presence of significant proteinuria. Low T4 values, when found in renal insufficiency, may be secondary to low serum albumin and possibly prealbumin.