Thyrotoxic crisis is an uncommon medical emergency caused by an exacerbation of hyperthyroidism characterised by decompensation of one or more organ systems in people with untreated or poorly treated hyperthyroidism.¹ Early recognition and aggressive treatment are essential. Thyroid storm can occur in patients with a toxic adenoma or multinodular toxic goitre, but is more often seen in patients with Graves' disease.

Presentation

Often sudden onset of severe hyperthyroidism with:^2,3

• Hyperpyrexia (over 41°C, dehydration)
• Heart rate greater than 140 beats per minute (with or without atrial fibrillation or other arrhythmia), hypotension, atrial dysrhythmias, congestive heart failure
• Nausea, jaundice, vomiting, diarrhoea, abdominal pain
• Confusion, agitation, delirium, psychosis, seizures or coma

Precipitants

Thyroid storm is most often seen in a thyrotoxic patient with intercurrent illness, trauma or emergency surgery. Common precipitants include:⁴

• Infection or other acute illness
• Withdrawal of or non-compliance with anti-thyroid medication
• Recent trauma, including surgical stress
• Myocardial infarction or stroke
• Diabetic ketoacidosis or hypoglycaemia
• Following childbirth⁵
• Pulmonary embolism
• Drugs: radio-iodine, amiodarone, radiographic contrast media
• Overdose of thyroid hormone tablets
• Recent thyroid surgery⁶

Investigations

• Investigations for any underlying precipitant, e.g. infection screen
• Thyroid function tests: elevated T3 and T4 levels, elevated T3 uptake, suppressed TSH levels
• Indications of decompensation of homeostasis, e.g. renal dysfunction, elevated creatinine kinase, electrolyte imbalance (due to dehydration), anaemia, thrombocytopenia, raised white cell count, abnormal liver function tests (raised levels of transaminases, lactate dehydrogenase, alkaline phosphatase and bilirubin), hypercalcaemia, hyperglycaemia
• ECG
• Chest X-ray
• Arterial blood gases and pH

Treatment

• Treatment of precipitating cause, e.g. any suspected infection.
• Resuscitation: oxygen, intravenous access and give 0.9% saline infusion (adjust IV fluids as necessary, ideally guided by central venous pressure), nasogastric tube if vomiting.
• Antithyroid treatment:
  • Carbimazole or propylthiouracil orally. After 4 hours give Lugol's solution (aqueous iodine oral solution).
  • Beta blockers (initially intravenous propranolol 5 mg, then orally) unless contra-indicated (e.g. asthma - but heart failure is not a contra-indication). Diltiazem can be used if propranolol is contra-indicated.
  • Intravenous hydrocortisone - blocks T4 to T3 conversion.
• For severe agitation, sedate with chlorpromazine.
• Keep cool with tepid sponging and with paracetamol. Avoid aspirin which can increase T4.
• Treat heart failure:
  • High-dose digoxin may be needed.
  • Cardioversion will not be effective for atrial fibrillation until the patient is euthyroid.
  • Give furosemide or bumetanide as required, depending on degree of pulmonary oedema and of dehydration.
• Anticoagulation: prophylactic subcutaneous heparin to prevent thromboembolism; intravenous infusion if in atrial fibrillation.
• If patient fails to improve within 1-2 days, may need to consider exchange transfusion, peritoneal dialysis or haemodialysis.
• Further thyroid management will depend on the progress of each individual patient and must be under the care of an endocrinologist.

Prognosis

• Untreated thyrotoxic crisis is usually fatal.⁶
• Even with early diagnosis and treatment the mortality is still 20-50%.⁷

Prevention

Identification and prevention or early treatment of precipitating factors.