Alterations in Serum Thyroid Hormones and Thyroxine-Binding Globulin in Patients with Nephrosis*

Serum concentration, T4-binding capacity, and affinity of thyroxine-binding globulin (TBG) were studied in 10 adult males with the nephrotic syndrome who were not receiving corticosteroid therapy. There was a significant correlation (r =-0.81,P<0.001) between the degree of proteinuria and the daily urinary excretion of TBG. The only subject who showed low serum TBG concentration and capacity had the severest degree of proteinuria (24 g⁄day). In all of the other patients the serum concentration and T4-binding capacity of TBG were within the normal range despite significant urinary losses of TBG. There was a tendency to lower TBG affinity values for T4 as compared to the control group, but the mean did not reach statistical significance. The nephrotic group as a whole exhibited an abnormally high fraction of dialyzable T4 and free T4 concentration in serum, but the mean total serum T4 was normal. The mean urinary excretion of T4 was 69 μ⁄day. Only two cases had low total serum T4, one of these having a low serum TBG concentration. There was a positive correlation (r =±0.53, P<0.001) between (the degree of proteinuria and daily urinary T4 loss. An inverse correlation (r = −0.68, P <0.02) was noted between the fraction of dialyzable T4 and the TBG affinity for 4. The mean total serum T3 was low, as was the T3⁄T4 ratio, suggesting an impaired peripheral conversion of T4 to T3. However, rT3 levels were normal. Serum thyrotropin concentrations were not elevated. Thus,in the nephrotic patients of the present study euthyroidism is probably maintained by a normal or slightly elevated free T4concentration. (J Clin Endo-crinol Metab46: 125, 1978)