What are the precipitating events of a thyroid storm?

Precipitating Events of Thyroid Storm

Thyroid storm is most commonly precipitated by acute stressors such as infection, surgery (including thyroid surgery), trauma, acute iodine load, discontinuation of antithyroid medication, and labor/delivery. 1, 2

Common Precipitating Factors

Medical Conditions and Procedures

• Infections: One of the most common triggers 2
• Surgery: Both thyroidal and non-thyroidal procedures 3
• Trauma: Including direct trauma to the thyroid 4
• Labor and delivery: Can trigger thyroid storm in pregnant women with uncontrolled hyperthyroidism 1
• Iodine exposure:
  • Radioiodine contrast media 4
  • Iodine-131 treatment 5
  • CT scans with iodinated contrast (exposing patients to 14-35 million mcg of iodine compared to the recommended daily intake of 150 mcg) 4

Medication-Related Factors

• Discontinuation of antithyroid drugs: Currently the most common precipitating factor 3
• Irregular use of antithyroid medications: Poor adherence to prescribed regimens 3

Clinical Presentation

Thyroid storm presents with exaggerated manifestations of hyperthyroidism and evidence of multiorgan decompensation:

• Fever: Often high-grade
• Cardiovascular: Tachycardia out of proportion to fever, heart failure, arrhythmias 1
• Neurological: Altered mental status (nervousness, restlessness, confusion, seizures) 1
• Gastrointestinal: Vomiting, diarrhea 1, 2
• Hepatic dysfunction: May be present 2

Diagnosis

Diagnosis is primarily clinical, based on a combination of signs and symptoms in a patient with known or suspected hyperthyroidism, especially following an identifiable precipitating event. Laboratory confirmation includes:

• Suppressed TSH
• Elevated free T4 and/or T3 levels 1

Clinical scoring systems like the Burch-Wartofsky point scale or Japan Thyroid Association diagnostic criteria can help establish the diagnosis 2.

Management

Treatment should be initiated immediately without waiting for laboratory confirmation 1:

1. Thionamides: Propylthiouracil (preferred initially due to its additional benefit of blocking T4 to T3 conversion) or methimazole 1, 6
2. Iodine solutions: Saturated solution of potassium iodide or sodium iodide (given 1 hour after thionamides to prevent iodine utilization for hormone synthesis) 1
3. Beta-blockers: To control cardiovascular symptoms 7
4. Corticosteroids: Dexamethasone to block peripheral conversion of T4 to T3 1
5. Supportive care: Oxygen, antipyretics, appropriate monitoring 1
6. Treatment of the underlying precipitant: Critical for resolution 2

Special Considerations

• In pregnant women, propylthiouracil is preferred in the first trimester, while methimazole is preferred in the second and third trimesters 8
• For refractory cases not responding to conventional therapy, therapeutic plasma exchange may be considered 9
• Delivery during thyroid storm should be avoided unless absolutely necessary 1

Prevention

• Patients with known hyperthyroidism should maintain strict adherence to antithyroid medications
• Patients requiring surgery should be in a euthyroid state before the procedure when possible 3
• Caution should be exercised when administering iodinated contrast to patients with known or suspected thyroid disease 4

Recognizing these precipitating factors and maintaining a high index of suspicion in at-risk patients is crucial for early diagnosis and management of this potentially fatal condition.