Thirty-eight patients with chronic renal insufficiency who were in a dialysis 
program underwent studies of thyroid function and metabolic status. Mean values 
for serum total and free thyroxine (T4) concentrations and thyroxine-binding 
globulin capacity were within normal limits. Although mean serum total 
triiodothyronine (T3) concentration was normal, 43% of the group had low serum 
T3 and 54% had low serum free T3 concentrations. Serum thyrotrophin (TSH) 
concentrations were normal in all but four subjects who had very slight 
elevations. Metabolic status was assessed by various metabolic tests; mean 
values for each of these tests were normal, and the clinical index scores 
indicated that all patients were euthyroid. Results of metabolic testing were 
similar in patients with low and those with normal serum T3 concentrations. Low 
serum T3 measurements did not accurately reflect metabolic state in patients 
with chronic renal failure, whereas serum free T4 and TSH concentrations were 
reliable indicators of thyroid state.