Impairment of Thyroid Function in Critically Ill Patients in the Intensive Care Units

Abstract

Unexplained hypotension in the intensive care unit is commonly attributed to volume depletion, cardiorespiratory failure, sepsis, or relative adrenal insufficiency. In these acute conditions, thyroid hormone levels measured in blood, serum or plasma are often altered and solely attributed to critical illness. We report a series of 3 critically ill patients with prolonged respiratory failure, suppressed mental status and unexplained hypotension. Thyroid stimulating hormone levels ranged from normal to mildly elevated (2.36-7.65IU/mL; normal: 0.27-4.20), but free thyroxin was markedly suppressed (0.239-0.66ng/dL; normal: 0.93-1.70). After initiation of intravenous levothyroxine (75-100μg/day), the patients could be weaned off vasopressors and were successfully extubated shortly thereafter. These cases demonstrate that hypothyroid intensive care unit patients may exhibit even seemingly normal or mildly abnormal thyroid stimulating hormone 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.

Keywords: Abnormal thyroid function tests; Levothyroxine; Sepsis; Shock; Thyroid stimulating hormone.