Myxedema Coma

Myxedema coma is life-threatening decompensated hypothyroidism with altered mental status and multiorgan dysfunction. The name is misleading: the patient does not need to be comatose. New confusion, increasing lethargy, somnolence, or reduced consciousness can mark this emergency. Older adults are most often affected, and lethargy or somnolence may worsen over weeks or months. Thyroid hormone supports metabolism and the function of nearly every organ system. With profound deficiency, heat production, ventilatory drive, cardiac performance, gastrointestinal motility, kidney function, and cerebral function all decline. Hypoventilation can cause hypoxemia and carbon dioxide retention; reduced cardiac output contributes to poor tissue perfusion; and impaired water handling can contribute to hyponatremia. Hypoglycemia can further impair consciousness. The combined failure, rather than one isolated laboratory abnormality, makes the condition immediately life-threatening. Most patients have established hypothyroidism. Missed levothyroxine, cold exposure, infection, stroke, a cardiac event, gastrointestinal bleeding, or sedating medicines can precipitate decompensation. The precipitant must be identified and treated at the same time as the hormone deficiency. Infection may be present without the expected fever or tachycardia, so absence of those responses does not...