Concentrations of thyrotropin, total thyroxine, total tri-iodothyronine and cortisol were measured on admission to an intensive care unit in 200 consecutive patients who did not receive dopamine. Thyrotropin concentration was subnormal (< 0.4 mU.l-1) in 25 patients (12%) and increased (> 5.0 mU.l-1) in 27 (13%). Mortality in these groups differed 22-fold (88% and 4% respectively) despite comparable APACHE II outcome predictions (51% and 32%). Thyrotropin concentration correlated positively with total thyroxine concentration (r = 0.46, p < 0.001) and negatively with cortisol concentration (r = -0.56, p < 0.001). In 15 of the patients with increased thyrotropin concentration on admission, repeat measurements were made on recovery and were normal in 13. The high frequency of abnormal thyrotropin concentrations casts doubt on the assumption of euthyroidism in critical illness. Admission thyrotropin concentration is of prognostic value in critically ill patients.
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