Thyroid status in patients with chronic renal failure.

Serum thyroid hormone concentrations have been measured in 21 patients with chronic renal failure, treated conservatively and compared with values from 19 control subjects. Many patients had serum total T3 and T4 concentrations below the reference ranges. The concentrations of free T4 and free T3 and the free thyroxine index were significantly lower in patients with abnormal total concentrations of the thyroid hormones than in the controls. Both the free and the total concentrations of T4 correlated inversely with the degree of renal failure. The concentration of thyroxine binding globulin (TBG), fell within the reference range in each of the patients, but was significantly lower in the patient group when compared with the controls. These TBG concentrations, however, were not sufficiently decreased to explain the low total thyroid hormone concentrations found in the patients. The affinity of TBG for T4 and T3 in the patient and control groups was not significantly different. The TSH response to TRH was diminished in many of the patients, but the measurement of other pituitary hormones indicated that pituitary function was normal in these patients. The possible mechanisms responsible for the changes observed in thyroid and pituitary hormones are discussed.