Function of the hypothalamo-hypophysial-thyroid axis in chronic renal failure

Hypothalamo-hypophysial-thyroid function has been studied in twenty-five patients with chronic renal failure. Eight were receiving conservative treatment, nine peritoneal dialysis and eight haemodialysis. All were clinically euthyroid. Total thyroxine (T4) and triiodothyronine (T3) levels were reduced but free T4 levels were normal, while free T3 was reduced in patients with the most severe renal failure. It is suggested that the binding of thyroid hormones by the transport proteins is reduced and that peripheral conversion of T4 to T3 is impaired in renal failure. The thyrotrophin response to thyrotrophin-releasing hormone (TRH) is reduced in renal failure but this reduction is probably independent of alterations in thyroid hormone metabolism. Growth hormone was released by TRH in seven of the patients studied, possibly as a result of protein malnutrition.