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Thyroid Storm

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Definition & Pathophysiology

• Sudden elevation of free thyroid hormones (T3/T4 released from binding proteins during stress)
• Increased adrenergic receptor sensitivity to circulating catecholamines
• Peripheral T4 → T3 conversion surge, amplifying active hormone levels
• T3 enters cell nuclei, binds thyroid hormone-responsive elements, drives widespread gene transcription and metabolic acceleration

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Precipitating Factors

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Clinical Features

• Hyperpyrexia: 104-106°F (40-41°C), often dramatic

• Tachycardia (often out of proportion to fever), atrial fibrillation
• Congestive heart failure, pulmonary edema, pedal edema
• Bibasal crepitations, hypotension (from volume depletion or cardiogenic shock)

• Agitation, anxiety, tremor
• Delirium, psychosis
• Seizures, extreme lethargy, coma

• Nausea, vomiting, diarrhea
• Abdominal pain
• Hepatic failure with jaundice (poor prognostic sign)

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Diagnosis

Burch-Wartofsky Point Scale (BWPS)

• Score ≥45: thyroid storm (or impending storm) - treat aggressively
• Score 25-44: impending storm - treat and monitor closely
• Score <25: unlikely thyroid storm

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Differential Diagnosis

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Management

Step 1 - Block peripheral T4 → T3 conversion (immediate)

• Propranolol 60-80 mg PO q4h OR 0.5-1.0 mg IV slow push test dose, then 1-2 mg IV q15 min until controlled, then 1-2 mg IV q3h
• Esmolol 50-100 mcg/kg/min IV infusion (preferred in heart failure - titratable)
• Metoprolol 25-50 mg PO q6h (alternative)
• If beta-blockers strictly contraindicated: reserpine 2.5-5 mg IM q4h OR diltiazem IV

• Hydrocortisone 300 mg IV loading dose, then 100 mg IV q8h
• OR Dexamethasone 2-4 mg IV q6h

Step 2 - Inhibit thyroid hormone synthesis (give 1 hour BEFORE iodide)

• PTU (propylthiouracil) 500-1000 mg loading dose PO/NG, then 250 mg q4h - preferred in storm because it also blocks peripheral T4→T3 conversion
• OR Methimazole 60-80 mg/day in divided doses
• Can be given PO, nasogastric, or PR (rectal enema prepared by pharmacy) - same dosing for all routes

Critical rule: ATD must be given at least 1 hour before iodide - otherwise iodide provides substrate for synthesis of even more thyroid hormone.

Step 3 - Inhibit thyroid hormone release (give AFTER ATD)

• SSKI (saturated solution of KI, 50 mg iodide/drop): 1-2 drops PO/PR three times daily
• OR Lugol's solution (8 mg iodide/drop): 5-7 drops PO/PR three times daily
• OR Sodium iodide IV per endocrinology guidance
• If iodine allergy: Lithium carbonate 300 mg PO/NG q6h (blocks hormone release)
• Cholestyramine 1-4 g PO twice daily - blocks enterohepatic recirculation of thyroid hormone (useful in refractory cases)

Step 4 - Supportive care

• IV fluids: D5/0.9NS for volume resuscitation and glycogen replacement (thyroid hormone depletes glycogen)
• Fever control: Acetaminophen (NOT aspirin - aspirin displaces T4 from thyroid-binding globulin, worsening free hormone levels), cooling blankets, ice packs, fans, ice lavage
• Electrolyte replacement and nutritional support
• Lorazepam or diazepam for agitation/seizures and to reduce central sympathetic outflow
• Supplemental oxygen, cardiac monitoring

Step 5 - Identify and treat the precipitating event

• Empirical broad-spectrum antibiotics if infection cannot be ruled out
• Treat concurrent DKA, pulmonary embolism, MI as indicated

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Refractory/Escalation Options

• Plasma exchange (plasmapheresis) - directly removes circulating T3/T4 and TSH-receptor antibodies (TRAbs)
• Dialysis - transient reduction of thyroid hormone levels
• Near-total thyroidectomy - only if ATDs are contraindicated (e.g., agranulocytosis), requires stabilization first

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Special Population: Pregnancy

• PTU is preferred over methimazole in the first trimester (methimazole has teratogenic risk - aplasia cutis, choanal atresia)
• Avoid aspirin - displaces thyroid hormones from TBG
• Short-acting beta-blockers preferred (e.g., esmolol, labetalol)
• Avoid delivery during active thyroid storm - fetal status typically improves as maternal status stabilizes
• Hydrocortisone is preferred over dexamethasone in pregnancy (largely inactivated by placental 11β-HSD to cortisone, reducing fetal exposure)

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Causes of Death

• Multiorgan dysfunction syndrome
• Congestive heart failure / high-output cardiac failure
• Cardiac arrhythmias
• Respiratory failure
• Disseminated intravascular coagulation (DIC)
• Hypoxic brain injury
• Sepsis
• Hepatic failure (jaundice = poor prognosis)

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Key Pearls

1. Clinical diagnosis - never delay treatment waiting for thyroid function tests
2. ATD before iodide - giving iodide first causes a surge in hormone synthesis
3. Avoid aspirin for fever - use acetaminophen only
4. PTU preferred over MMI in storm - dual benefit of synthesis inhibition AND peripheral conversion block
5. Burch-Wartofsky ≥45 = treat as storm regardless of lab values
6. Mortality is 10-30% even with treatment; unrecognized storm carries up to 75% mortality
7. Esmolol preferred over propranolol in heart failure (short-acting, easily titrated, reversed)

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