Thyroid storm (thyroid crisis) is a rare but life-threatening endocrine emergency resulting from severe exacerbation of thyrotoxicosis. It is characterized by systemic decompensation rather than simply markedly elevated thyroid hormone levels and requires immediate recognition and aggressive multimodal treatment in an intensive care setting.

Pathophysiology

Thyroid storm occurs when excessive circulating thyroid hormones, together with a precipitating event, produce overwhelming metabolic and adrenergic effects that result in cardiovascular, neurological, gastrointestinal, and thermoregulatory dysfunction. The severity of illness is related to systemic decompensation rather than the absolute thyroid hormone concentration.

Triggers

Common precipitating factors include:

• Withdrawal of antithyroid medication

• Acute infections

• Thyroid surgery

• Non-thyroid surgery

• Iodinated contrast media

• External beam radiation therapy

Thyroid storm should be suspected in any critically ill patient with a recent history of thyrotoxicosis and an identifiable precipitating factor.

Clinical features

Patients may present with:

• Tachycardia

• Cardiac arrhythmias

• Congestive heart failure

• Hypotension

• Hyperpyrexia

• Agitation

• Delirium

• Psychosis

• Confusion

• Stupor

• Coma

• Nausea

• Vomiting

• Diarrhoea

• Hepatic failure

Diagnostic criteria

Diagnosis is primarily clinical and should not be delayed while awaiting laboratory confirmation. Thyroid storm should be considered in patients with severe systemic illness, known or suspected thyrotoxicosis, and recent exposure to a precipitating factor.

Investigations

• Serum TSH

• Free T4 and T3

• Complete blood count

• Liver function tests

• Serum electrolytes

• Renal function tests

• Blood glucose

• Electrocardiogram (ECG)

• Chest X-ray when infection or heart failure is suspected

• Blood cultures and other investigations to identify the precipitating cause

Management

Thyroid storm is a medical emergency requiring admission to an intensive care unit and prompt multimodal treatment.

Non-pharmacological management

• Admit to an intensive care unit.

• Initiate aggressive cooling using cooling blankets and acetaminophen.

• Provide intravenous fluid resuscitation.

• Provide respiratory support as required.

• Continuously monitor cardiovascular and respiratory status.

• Identify and treat the underlying precipitating cause.

Pharmacological management

Treatment should be instituted promptly using the following therapies:

Antithyroid medicine

Propylthiouracil is preferred in thyroid storm.

• Propylthiouracil 500–1000 mg loading dose, followed by 250 mg every 4 hours.

  • Blocks new thyroid hormone synthesis.

  • Inhibits peripheral conversion of T4 to T3.

Alternative

• Carbimazole 40–60 mg/day orally.

  • Blocks new thyroid hormone synthesis.

Beta-adrenergic blockade

• Propranolol 60–80 mg every 4 hours.

  • Controls adrenergic manifestations.

  • High doses also reduce peripheral conversion of T4 to T3.

  • Consider invasive haemodynamic monitoring in patients with congestive heart failure.

  • Esmolol infusion may be used as an alternative where appropriate.

Inorganic iodide

Administer at least one hour after antithyroid medicine.

• Saturated solution of potassium iodide 5 drops (0.25 mL or 250 mg) orally every 6 hours.

  • Inhibits new thyroid hormone synthesis.

  • Blocks release of stored thyroid hormones.

Corticosteroids

• Hydrocortisone 300 mg intravenous loading dose, followed by 100 mg every 8 hours.

  • Reduces peripheral conversion of T4 to T3.

  • Provides prophylaxis against relative adrenal insufficiency.

  • Dexamethasone may be used as an alternative.

Monitoring

• Continuous cardiac monitoring

• Frequent assessment of blood pressure and heart rate

• Continuous temperature monitoring

• Regular monitoring of serum electrolytes and blood glucose

• Liver and renal function tests

• Fluid balance and urine output

• Serial thyroid function tests during recovery

Complications

• Cardiac arrhythmias

• Congestive heart failure

• Cardiogenic shock

• Acute hepatic failure

• Respiratory failure

• Multi-organ failure

• Coma

• Death

Prognosis

Thyroid storm carries a high mortality if treatment is delayed. Early recognition, prompt initiation of multimodal therapy, intensive supportive care, and treatment of the precipitating cause markedly improve survival. Long-term prognosis is generally good once euthyroidism is achieved and the underlying thyroid disorder is definitively managed.