Thyroid Storm
Endocrinology
Illness script · Endocrinology
Thyroid Storm
Life-threatening hypermetabolic crisis from extreme thyroid hormone excess, typically precipitated by physiologic stress in undertreated hyperthyroidism.
This illness script for Thyroid Storm covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Underlying Graves' disease most common (also toxic MNG, toxic adenoma)
- Precipitants: infection, surgery, trauma, iodine load (contrast), labor/delivery
- Abrupt discontinuation of antithyroid medications
- Radioiodine therapy in unprepared patients
- More common in women; rare but mortality ~10–30% even with treatment
02
Presentation
- Burch-Wartofsky criteria: hyperthermia (>38.5°C), tachycardia (often >140 bpm), CNS dysfunction
- CNS: agitation, delirium, psychosis, seizure, or coma
- GI: nausea, vomiting, diarrhea, jaundice (poor prognostic sign)
- Cardiovascular: afib, high-output heart failure, wide pulse pressure
- Diaphoresis, goiter, exophthalmos often present (underlying Graves')
- Timeline: develops over hours following precipitant
03
Pathophysiology
- Massive surge in free T3/T4 → exaggerated catecholamine sensitivity
- Increased beta-adrenergic receptor density amplifies sympathetic effects
- Excess thyroid hormone → uncoupled oxidative phosphorylation → hyperthermia
- Rapid hormone release (not just synthesis) accounts for acute onset
04
Diagnostics
- Diagnosis is CLINICAL — Burch-Wartofsky score ≥45 highly suggestive
- TSH suppressed (<0.01); free T4/T3 elevated (but levels don't distinguish from uncomplicated hyperthyroidism)
- CBC, LFTs, cultures to identify precipitating infection
- ECG: afib common
- Pearl: degree of hormone elevation does NOT predict storm — clinical picture drives diagnosis
05
Management
- Step 1: PTU (preferred over methimazole) — blocks new synthesis AND peripheral T4→T3 conversion
- Step 2: Iodine (SSKI/Lugol's) given ≥1 hour AFTER PTU to block hormone release (Wolff-Chaikoff)
- Step 3: Beta-blocker (propranolol IV preferred) — controls sympathetic symptoms, also inhibits T4→T3
- Step 4: Hydrocortisone — reduces T4→T3 conversion, covers relative adrenal insufficiency
- Treat precipitant; ICU admission mandatory; cholestyramine as adjunct to reduce enterohepatic recycling
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Uncomplicated thyrotoxicosis
Thyroid storm has CNS dysfunction + hyperpyrexia + multi-organ involvement; labs alone cannot differentiate
Neuroleptic malignant syndrome
NMS: antipsychotic exposure, lead-pipe rigidity, bradyreflexia — no goiter or elevated T4
Serotonin syndrome
Serotonin syndrome: serotonergic drug exposure, clonus/hyperreflexia, onset within hours of drug change
Sepsis with delirium
Sepsis lacks goiter, exophthalmos, exaggerated sympathetic surge; TSH/T4 identify thyroid storm
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.