Diagnosing Thyroid Storm
Thyroid storm is a clinical diagnosis that should never be delayed for laboratory confirmation—immediately initiate treatment when clinically suspected based on the presence of severe hyperthyroidism with fever, tachycardia disproportionate to fever, altered mental status, gastrointestinal symptoms, and evidence of multiorgan decompensation. 1, 2
Clinical Diagnostic Criteria
The diagnosis relies on recognizing the constellation of severe clinical features, not laboratory values alone:
Core Clinical Features (Must Be Present)
- Fever (often >38.5°C/101.3°F) 1, 3
- Tachycardia disproportionate to the degree of fever (often >140 bpm) 1, 3
- Central nervous system dysfunction: altered mental status, agitation, delirium, psychosis, seizures, or coma 1, 3
- Gastrointestinal symptoms: nausiting, vomiting, diarrhea, abdominal pain, or hepatic dysfunction 1, 3
- Cardiovascular manifestations: cardiac arrhythmias (especially atrial fibrillation), congestive heart failure, or signs of high-output cardiac failure 1, 3
Structured Scoring Systems
Two validated clinical scoring systems exist to formalize the diagnosis:
- Burch-Wartofsky Point Scale: Assigns points based on temperature, CNS effects, cardiovascular dysfunction, gastrointestinal-hepatic dysfunction, and precipitating event; score ≥45 is highly suggestive of thyroid storm 3, 4
- Japan Thyroid Association Diagnostic Criteria: Requires thyrotoxicosis plus specific combinations of CNS, cardiovascular, and gastrointestinal manifestations 5
Laboratory Assessment
Critical point: No single laboratory value establishes the diagnosis of thyroid storm, and severely ill patients may paradoxically not have the highest thyroid hormone levels. 1, 6
Essential Initial Tests (Do Not Delay Treatment)
- Serum TSH: Typically suppressed (<0.01 mU/L) 6, 2
- Free T4 (FT4): Elevated 6, 2
- Free T3 (FT3): May be elevated, but the FT3/FT4 ratio may inversely correlate with disease severity 1, 6
- Complete blood count: To evaluate for agranulocytosis and assess for infection as a trigger 6
Additional Supportive Tests
- Thyroid peroxidase (TPO) antibody: Helps distinguish between different causes of thyrotoxicosis 6
- Liver function tests: To assess for hepatic dysfunction, a common feature of thyroid storm 6
- Electrolytes, glucose, calcium: To identify metabolic derangements 3
Identifying Precipitating Factors
Always search for the inciting trigger, as thyroid storm rarely occurs spontaneously:
- Infection (most common trigger) 3, 5
- Surgery or trauma (including direct thyroid gland injury) 7
- Acute medical illness (myocardial infarction, stroke, diabetic ketoacidosis) 3, 4
- Medication noncompliance with antithyroid drugs 4
- Iodine exposure (contrast agents, amiodarone) 3
- Pregnancy-related (labor, delivery, cesarean section) 4
- Immunotherapy (checkpoint inhibitors like nivolumab/ipilimumab) 8
Critical Diagnostic Pitfalls
Do Not Confuse With These Mimics
Thyroid storm shares features with several other emergencies that must be considered in the differential:
- Sympathomimetic overdose (cocaine, amphetamines) 3
- Alcohol withdrawal 3
- Serotonin syndrome 3
- Sepsis/septic shock 3
- Heat stroke 3
- Acute pulmonary edema or aortic dissection 3
Key Distinguishing Features
- History of hyperthyroidism or thyroid disease strongly supports thyroid storm 3, 4
- Presence of goiter or exophthalmos on physical examination 3
- Disproportionate tachycardia relative to fever (unlike sepsis where they correlate) 1
Diagnostic Algorithm
- Recognize the clinical syndrome: Severe hyperthyroid symptoms + fever + altered mental status + cardiovascular instability 1, 2
- Apply Burch-Wartofsky or JTA criteria to formalize suspicion 3, 5
- Draw blood for TSH, FT4, FT3, CBC, and other supportive tests 6, 2
- Immediately initiate treatment WITHOUT waiting for laboratory results 1, 6, 2
- Identify and treat the precipitating factor 3, 5
Special Populations
Pregnant Patients
- Same diagnostic approach applies with TSH, FT4, and FT3 2
- Add fetal monitoring (ultrasound, nonstress testing, biophysical profile) 6, 2
- Avoid delivery during active thyroid storm unless absolutely necessary 1