What is thyroid storm according to American Thyroid Association (ATA) guidelines in an adult patient with a history of hyperthyroidism, possibly with Graves' disease?

Thyroid Storm Definition and Diagnostic Criteria

Thyroid storm is a life-threatening medical emergency characterized by the clinical triad of severe hyperpyrexia (fever often >104°F/40°C), extreme tachycardia (typically >140 bpm), and altered mental status ranging from agitation to coma in a patient with known or suspected hyperthyroidism. 1

Clinical Diagnosis

• The diagnosis must be made entirely on clinical grounds without waiting for laboratory confirmation, as thyroid hormone levels do not differ between uncomplicated thyrotoxicosis and thyroid storm 2, 3, 4
• No laboratory tests are diagnostic or specific for thyroid storm 3, 4
• Any delay in treatment while awaiting laboratory results must be strictly avoided, as mortality can rise to 75% with delayed treatment 2

Core Clinical Features

Cardiovascular Manifestations

• Severe tachycardia with heart rate typically exceeding 140 bpm 1
• Atrial fibrillation and other arrhythmias 1
• Hypertension or hypotension depending on severity 1
• Congestive heart failure and cardiogenic shock in severe cases 1

Thermoregulatory Dysfunction

• Marked hyperpyrexia with fever often exceeding 104°F (40°C) 1
• Profuse sweating and severe heat intolerance 1

Neuropsychiatric Features

• Altered mental status is a defining feature, ranging from extreme agitation and nervousness to delirium and coma 1, 3
• Striking alterations in consciousness 3

Gastrointestinal Symptoms

• Severe diarrhea 1
• Dramatic worsening of baseline hyperthyroidism symptoms including weight loss and muscle weakness 1

Multiorgan System Decompensation

• Thyroid storm represents multiorgan system failure including cardiovascular collapse, renal insufficiency, and coagulopathy 1
• The condition affects less than 1-2% of patients with overt hyperthyroidism 5, 2

Mortality and Prognosis

• Mortality reaches 75% if treatment is delayed and 30% even with appropriate treatment 1
• More recent series report mortality rates between 10-20% with prompt recognition and aggressive management 2, 4
• The underlying precipitating cause is a major determinant of survival 3

Common Precipitating Factors

• Infection (most common trigger) 1, 6
• Medication non-adherence in known hyperthyroid patients 1, 6
• Acute medical illness or surgery 1, 2
• Pregnancy, labor, and delivery 5, 1
• Trauma 6

Key Clinical Pitfall

The most critical error is delaying treatment while awaiting thyroid function test results, as the diagnosis is clinical and immediate therapy is essential for survival 2, 3. Treatment must be initiated immediately upon clinical suspicion in any hyperthyroid patient presenting with the characteristic triad of hyperpyrexia, extreme tachycardia, and altered mental status 1.