Prospective study on thyroid function anomalies in severely ill patients.

Patients with severe non-thyroidal illness (NTI) often evidence concomitant anomalies in thyroid function (TF). In order to shed light on the implications of these anomalies and/or changes and disease course, we monitored TF changes in a selected cohort of 45 patients with serious NTI (21 with liver cirrhosis, 15 with renal failure and 9 with malignancy) from April 1985 to October 1989. TF test results on admission were as follows: all patients had normal thyroid stimulating hormone (TSH) levels; 16 patients had no TF abnormalities; 28 had decreased serum triiodothyronine (T3) and increased serum reverse triiodothyronine (rT3) levels, (8 of them had low serum free T3 values as well); 1 patient had subnormal level of both T3 and thyroxine (T4). Fifteen (53.5%) of the 28 subjects with initial low T3 sustained a subsequent decline in total and free serum T4 to subnormal levels; in 13 of these patients the drop occurred shortly before death. Patients in critical condition with below normal serum T4 also had decreased serum TSH concentrations: the so-called "low T3 and low T4 syndrome" might thus result from decreased TSH concentrations: due to failure of the usual feedback mechanism. Eighteen patients (40%) had died by the end of the study period. The mortality rate was 89% in patients with initial T3 level less than 0.40 nmol/L. This finding leads us to the hypothesis that initial low T3 levels in NTI patients are indicative of a poor prognosis.