Thyroid function was measured in 86 patients hospitalized in an intensive care unit. Two patients were found to have primary hypothyroidism and were excluded from the study. Hypothyroxinemia with normal thyroidstimulating hormone (TSH) levels was found in 22% of the patients and was associated with a high mortality (thyroxine [T4] levels less than 3.0 μg/DL, 84% mortality; T4 levels of 3.0 to 5.0 γg/DL, 50% mortality; and T4 levels greater than 5.0 γg/DL, 15% mortality). There was a high correlation between low T4 levels and mortality.
Slag MF, Morley JE, Elson MK, Crowson TW, Nuttall FQ, Shafer RB. Hypothyroxinemia in Critically III Patients as a Predictor of High Mortality. JAMA. 1981;245(1):43-45. doi:10.1001/jama.1981.03310260021020