What is a thyroid storm?

Thyroid Storm: A Life-Threatening Medical Emergency

Thyroid storm is a rare but life-threatening hypermetabolic state characterized by extreme manifestations of thyrotoxicosis with multiorgan decompensation, carrying a mortality rate of up to 30% if not promptly recognized and treated. 1

Definition and Clinical Features

Thyroid storm represents the severe end of the thyroid dysfunction spectrum, characterized by:

• Core clinical manifestations:

  • Fever (>100.4°F)
  • Tachycardia (often >100 beats/min)
  • Altered mental status/central nervous system dysfunction
  • Gastrointestinal symptoms (vomiting, diarrhea)
  • Evidence of heart failure
  • Hepatic dysfunction 2, 1

• Diagnostic criteria:

  • Burch-Wartofsky point scale
  • Japan Thyroid Association diagnostic criteria 1

Central nervous system dysfunction is the most significant clinical feature distinguishing true thyroid storm from severe but compensated thyrotoxicosis 3.

Epidemiology and Risk Factors

• Rare condition affecting a small percentage of patients with hyperthyroidism 4
• Highest incidence observed during summer months 5
• Usually occurs in the presence of a precipitating trigger or intercurrent illness 6
• Most commonly seen in patients with underlying Graves' disease 4

Pathophysiology

Thyroid storm involves:

• Extreme elevation of circulating thyroid hormones
• Propylthiouracil is particularly valuable as it inhibits both thyroid hormone synthesis and peripheral conversion of T4 to T3 7
• Sympathetic nervous system hyperactivity contributing to many clinical manifestations 8

Mortality Risk Factors

Higher mortality is significantly associated with:

• Age ≥60 years
• Central nervous system dysfunction at admission
• Nonuse of antithyroid drugs and β-blockers
• Requirement for mechanical ventilation
• Need for therapeutic plasma exchange with hemodialysis 5

Management

Immediate, aggressive treatment is essential:

1. Thionamides (first-line):

   • Propylthiouracil or methimazole to block new hormone synthesis
   • Propylthiouracil preferred in first trimester pregnancy and in thyroid storm (due to additional inhibition of T4 to T3 conversion) 2, 7

2. Iodine solutions:

   • Must be administered 1 hour AFTER thionamides to prevent increased hormone synthesis 2
   • Blocks release of preformed thyroid hormone

3. Beta-blockers:

   • Critical for controlling sympathetic hyperactivity
   • Propranolol particularly useful as it blocks both adrenergic effects and peripheral T4 to T3 conversion
   • May require high doses
   • Use with caution in severe heart failure 2, 8

4. Corticosteroids:

   • Dexamethasone recommended to reduce T4 to T3 conversion and treat potential adrenal insufficiency 2

5. Supportive care:

   • Oxygen therapy
   • Antipyretics for fever management
   • Cardiac monitoring
   • Fluid and electrolyte management
   • Identification and treatment of the precipitating trigger 2

Special Considerations

• Pregnancy: Propylthiouracil preferred in first trimester; delivery during thyroid storm should be avoided unless necessary 2

• Cardiac complications: Thyroid storm can present with heart failure and even venous thrombosis due to hypercoagulable state 9

• Differential diagnosis: Must distinguish from mimics including sympathomimetic overdose, substance use disorders, alcohol withdrawal, heat stroke, serotonin syndrome, and sepsis 1

Monitoring

• Close monitoring of vital signs and mental status
• Serial thyroid function tests
• Monitoring for treatment complications (e.g., hepatotoxicity with PTU) 2

Thyroid storm remains a clinical diagnosis requiring high suspicion in patients presenting with extreme manifestations of thyrotoxicosis, particularly when accompanied by central nervous system dysfunction and a precipitating event.