Serum reverse triiodothyronine and thyroxine kinetics in patients with chronic renal failure.

Abstract

Patients with chronic renal failure (CRF) have reduced serum total T3 (TT3) but normal total rT3 (TrT3) concentrations. These findings contrast with those of nonrenal nonthyroidal illnesses and malnutrition where low TT3 levels are associated with elevated TrT3 values. To evaluate the mechanisms for the normal TrT3 concentrations in CRF patients, iv bolus serum kinetic studies of labeled rT3 were carried out in 13 CRF and 8 normal subjects. In addition, T4 kinetics were studied in 7 CRF and 20 normal individuals. The CRF patients had normal or minimally reduced serum albumin [3.8 ± 0.2 (SE) g/dl] and transferrin (281 ± 17 mg/dl) levels and normal relative BW (95 ± 4%) and body mass index (23.0 ± 0.9 kg/m2) values, indicating adequate protein nutritional status. The mean serum TT3 levels were decreased to 62% of the normal mean (P < 0.001). There were significant increases in the mean values of the percent free fraction of rT3 (135% of normal mean, P < 0.001), free rT3 (131%, P < 0.001) and T4 binding glob...