Effect of chronic hemodialysis on thyroid function tests in patients with end-stage renal disease

In patients with end-stage renal disease (ESRD), serum concentrations of thyroid hormones are often found to be disturbed. The aim of the study was to evaluate the effect of chronic hemodialysis (CHD) on the regulation of decreased levels of thyroid hormones and thyroxine-binding globulin (TBG) in serum of patients with ESRD. This effect was analyzed during two phases of CHD in patients with ESRD. The first period of CHD (FCHD) lasted 14.6 months and the second period (SCHD) was prolonged by additional 16.7 months. The concentrations of thyroid hormones (T4, FT4, T3, FT3, rT3), thyrotropin (TSH) and TBG were determined in serum samples obtained before the patients started hemodialysis (BHD) and at the end of FCHD and SCHD. From the first group of 48 patients with ESRD who had previously been tested BHD, 28 patients received FCHD and only 10 of them continued to receive additional SCHD. The levels of all thyroid hormones were found to be decreased, especially some hormones such as FT3 (87% BHD), T3 (93% FCHD) and FT4/FT3 (90% SCHD). The concentration of TSH did not change significantly during CHD and about 10% of decreased and 10% of increased values were recorded. Only TBG level from decreased values (37% BHD) returned to the normal range at the end of SCHD. Results of rT3 could not be interpreted with certainty, because two different commercial kits were used during the study. Although CHD lasted for 31.3 months, it did not have any positive effect on the regulation of disturbed thyroid hormones to the normal levels.