Functional impairment of thyroid function in critically ill patients in the Intensive Care Units

Abstract Unexplained hypotension in the intensive care unit (ICU) is commonly attributed to volume depletion, cardiorespiratory failure, sepsis, or relative adrenal insufficiency. In these acute conditions, thyroid hormone levels measured in blood/serum/plasma are often altered and solely attributed to critical illness. We report a series of three critically ill patients with prolonged respiratory failure, suppressed mental status, and unexplained hypotension. Thyroid stimulating hormone (TSH) levels ranged from normal to mildly elevated (2.36–7.65 IU/mL; normal: 0.27–4.20), but free T4 was markedly suppressed (0.239–0.66 ng/dL; normal: 0.93–1.70). After initiation of intravenous levothyroxine (75–100 mcg/day), the patients could be weaned off vasopressors and successfully extubated shortly thereafter. These cases demonstrate that hypothyroid ICU patients may exhibit even seemingly normal or mildly abnormal TSH values. Early recognition and treatment of a hypothyroid state superimposed on critical illness may contribute to recovery from hypotension or the need for mechanical ventilation.