Summary

Myxoedema coma is a rare, life-threatening decompensation of severe hypothyroidism. Despite its name, patients are often obtunded rather than comatose. It typically occurs in elderly patients with undiagnosed or undertreated hypothyroidism after a precipitating event. Cardinal features include altered mental status, hypothermia, bradycardia, hypoventilation, and hyponatraemia. Treatment requires ICU admission, IV thyroid hormone replacement (T4 +/- T3), empirical hydrocortisone (to cover possible adrenal insufficiency), and supportive care. Mortality remains high at 30-60% even with treatment.

Key Facts

• Definition: Decompensated severe hypothyroidism with systemic failure
• Incidence: Very rare; peak in winter months
• Peak Demographics: Elderly women with undiagnosed/undertreated hypothyroidism
• Pathognomonic: Hypothyroidism + hypothermia + altered mental status
• Gold Standard Investigation: Clinical diagnosis + TFTs
• First-line Treatment: IV T4 +/- T3 + hydrocortisone + supportive
• Prognosis: Mortality 30-60%

Clinical Pearls

Emergency Pearl: Give hydrocortisone before or with thyroid hormone - thyroid replacement can precipitate adrenal crisis.

Temperature Pearl: Use passive rewarming only - active warming causes vasodilation and cardiovascular collapse.

Ventilation Pearl: Patients often have hypoventilation and CO2 retention - mechanical ventilation frequently required.

• Infection (most common)
• Cold exposure
• Sedatives, opioids
• Stroke
• Trauma
• GI bleeding
• Non-compliance with levothyroxine

Viva Points

"Myxoedema coma: altered mental status, hypothermia, bradycardia. Give steroids WITH thyroid hormone. Passive warming only. IV T4 +/- T3. High mortality."

Last Reviewed: 2026-01-01 | MedVellum Editorial Team