ICU · endocrine

Acute Thyroid Storm and Myxoedema Coma — Comprehensive Thyroid Emergencies

Also known as Thyroid storm · Thyrotoxic crisis · Thyrotoxic storm · Burch-Wartofsky Point Scale · Myxoedema coma · Myxedema coma · Decompensated hypothyroidism · Propylthiouracil (PTU) · Carbimazole · Wolff-Chaikoff effect · Jod-Basedow phenomenon · Lugol's iodine · IV levothyroxine · Liothyronine (T3)

Thyroid storm and myxoedema coma are the two life-threatening decompensated thyroid emergencies at opposite ends of the thyroid hormone spectrum. Thyroid storm (thyrotoxic crisis) = the extreme state of thyrotoxicosis with hyperthermia, tachyarrhythmia (including atrial fibrillation), neuropsychiatric/CNS disturbance, congestive heart failure and GI/hepatic dysfunction, usually occurring in the presence of an inciting trigger; diagnosis is clinical (published cohorts have used a Burch-Wartofsky score of ≥45 as the storm-defining inclusion threshold), as TFT results take days and the syndrome must be treated empirically. Common precipitants include infection (1), surgery, trauma, radioiodine therapy, withdrawal of antithyroid drugs, amiodarone, iodinated contrast, DKA, and parturition. Management is multimodal and stepwise — first-line thionamide plus beta-adrenergic blocker, FOLLOWED BY inorganic iodine, with corticosteroids and adjuncts (cholestyramine, plasmapheresis or emergent thyroidectomy in appropriately severely ill patients); published case protocols use PTU 1 g loading then 200 mg every 4 hours, or PTU 250 mg every 4 hours via nasogastric tube with hydrocortisone 100 mg intravenously every 8 hours and propranolol 50 mg every 4 hours via nasogastric tube; ultra-short-acting esmolol is safer than propranolol when cardiac failure complicates storm (oral propranolol preceded cardiorespiratory arrest in three published cases); antipyresis with paracetamol NOT aspirin (aspirin intoxication has itself precipitated storm) plus external cooling and treatment of the trigger. Myxoedema coma = decompensated severe hypothyroidism with impaired consciousness, hypothermia, hypoventilation and hypercapnic respiratory failure with CO2 narcosis, dilutional hyponatraemia, hypoglycaemia and ileus; management is IV levothyroxine (200-500 mcg initial dose then 50-100 mcg daily, concurrent T3 can be considered, most authorities prefer IV T4 over IV T3, and oral loading 300-500 mcg with taper over 3-5 days is effective where IV is unavailable), hydrocortisone until coexisting adrenal insufficiency is ruled out, passive rewarming with careful attention to hypotension, correction of electrolyte abnormalities, treatment of infections, and respiratory/haemodynamic support in ICU. Mortality of thyroid storm is 10-50% with treatment (80-100% without); myxoedema coma mortality is reported from about 20% to as high as 60%.

high30 referencesUpdated 2 Sept 202628 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

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IODINE IS ADDED ONLY AFTER THE THIONAMIDE IS ON BOARD, never as the first agent. Guidelines sequence initial therapy as thionamide plus beta-blocker first, with inorganic iodine following — iodine is never given as sole or first-line blockade (and observational data show iodine is used alongside antithyroid drugs as initial therapy). Iodine is never the opening agent: thionamide first, iodine after.
AVOID salicylates (aspirin) for antipyresis in thyroid storm. Aspirin overdose has itself precipitated thyroid storm (a published case was successfully treated with haemodialysis), and thyroid dysfunction is a recognised serious consequence of overdose of aspirin and other NSAIDs. Use paracetamol and active external cooling instead.
ALWAYS give hydrocortisone in myxoedema coma BEFORE or WITH levothyroxine. Coexisting adrenal insufficiency must be assumed until excluded — hydrocortisone is administered empirically to every myxoedema coma patient until adrenal insufficiency is ruled out, alongside treatment of infection, electrolyte correction, passive rewarming, and respiratory/haemodynamic support.
PASSIVE REWARMING in myxoedema coma (Myers): correction of electrolytes, passive rewarming, treatment of infections, respiratory and haemodynamic support, stress-dose glucocorticoids, and thyroid hormone replacement. Do not invent active-warming clocks.
PTU is the thionamide used in acute thyroid storm protocols (beneficial in thyroid storm and first-trimester pregnancy), but it carries an FDA black-box warning for severe hepatotoxicity — carbimazole/methimazole cause less severe hepatic injury and are preferred outside these two settings. High-dose PTU regimens also risk early agranulocytosis; published case protocols use PTU 1 g loading then 200 mg every 4 hours, or 250 mg every 4 hours, with hydrocortisone, propranolol and iodine, switching to carbimazole or definitive therapy when thionamide toxicity intervenes.
Beta-blockade in thyroid storm with coexisting heart failure is dangerous — oral propranolol preceded sudden cardiorespiratory arrest in three published cases, and in low-output cardiac failure complicating severe thyrotoxicosis it may be advisable to avoid beta-blockade altogether. Use short-acting esmolol (found safer than propranolol in a systematic literature review) or landiolol rather than long-acting propranolol, with haemodynamic monitoring; beta blockers are administered in the absence of severe heart failure.

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