Thyrotoxic Storm

Definition

Thyrotoxic storm, also known as thyroid storm, is a life-threatening condition characterised by an extreme and sudden exacerbation of hyperthyroidism symptoms. It is a medical emergency requiring prompt diagnosis and treatment to prevent severe complications and death.

Aetiology

Thyrotoxic storm can be triggered by several factors in patients with underlying hyperthyroidism:

Infection (e.g., pneumonia, sepsis)
Surgery or trauma
Discontinuation of antithyroid medications
Radioactive iodine therapy
Acute illness (e.g., myocardial infarction, stroke)
Pregnancy or childbirth

Pathophysiology

Thyrotoxic storm results from an acute increase in circulating thyroid hormones (thyroxine [T4] and triiodothyronine [T3]), leading to a hypermetabolic state. This surge in thyroid hormones causes widespread systemic effects:

Increased cardiac output and heart rate, leading to cardiovascular stress
Enhanced thermogenesis, resulting in hyperthermia
Excessive catabolism, causing muscle wasting and weight loss
Heightened central nervous system activity, leading to agitation and delirium

Risk Factors

Pre-existing hyperthyroidism (e.g., Graves' disease, toxic multinodular goitre)
Recent infection or acute illness
Non-compliance with antithyroid medications
Thyroid surgery or radioactive iodine treatment
Poorly controlled hyperthyroidism

Signs and Symptoms

Thyrotoxic storm presents with a constellation of severe symptoms:

Hyperthermia (fever)
Tachycardia (rapid heart rate), which may lead to atrial fibrillation
Hypertension followed by hypotension and shock
Agitation, anxiety, delirium, or psychosis
Nausea, vomiting, diarrhoea
Severe muscle weakness
Heart failure
Coma in advanced stages

Investigations

Clinical history and physical examination
Thyroid function tests: TSH (usually suppressed), free T4, and free T3 (elevated)
Electrolytes, urea, and creatinine: To assess renal function and electrolyte balance
Complete blood count (CBC): To identify any underlying infection
Arterial blood gas (ABG): To evaluate acid-base balance and oxygenation
Electrocardiogram (ECG): To detect cardiac arrhythmias
Chest X-ray: To identify any concurrent infection or heart failure

Management

Primary Care Management

Immediate referral to hospital: Thyrotoxic storm is a medical emergency requiring hospitalisation.
Stabilisation: Ensure airway, breathing, and circulation are supported while awaiting transfer.
Education: Inform patients and caregivers about the importance of medication adherence and recognising early symptoms of thyrotoxicosis.

Hospital Management

Antithyroid drugs: High-dose propylthiouracil (PTU) or methimazole to inhibit thyroid hormone synthesis.
Beta-blockers: Propranolol or esmolol to control tachycardia and reduce peripheral conversion of T4 to T3.
Iodine solution: Lugol's iodine or potassium iodide to inhibit the release of thyroid hormones.
Glucocorticoids: Hydrocortisone or dexamethasone to reduce thyroid hormone release and peripheral conversion, and to treat potential adrenal insufficiency.
Supportive care: Aggressive cooling for hyperthermia, rehydration with IV fluids, electrolyte correction, and treatment of any underlying infections or precipitating factors.
Monitoring: Continuous monitoring of vital signs, cardiac rhythm, and laboratory parameters to assess treatment response and detect complications.

Example Management for Thyrotoxic Storm

A patient presenting with a thyrotoxic storm should be immediately referred to the hospital for urgent management. Initial treatment includes high-dose propylthiouracil (PTU) to inhibit thyroid hormone synthesis, followed by iodine solution to block hormone release. Propranolol is administered to control tachycardia and reduce peripheral conversion of T4 to T3. Glucocorticoids such as hydrocortisone are given to further inhibit thyroid hormone release and treat potential adrenal insufficiency. Supportive care involves aggressive cooling measures, intravenous fluids for rehydration, and correction of electrolyte imbalances. Continuous monitoring of vital signs and laboratory parameters is essential to guide treatment and detect complications.

References

NICE. (2024). Hyperthyroidism: Assessment and Management. Retrieved from NICE
NHS. (2023). Thyroid Storm. Retrieved from NHS
American Thyroid Association (ATA). (2022). Guidelines for the Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Retrieved from ATA
British Thyroid Foundation. (2021). Thyroid Storm Information. Retrieved from British Thyroid Foundation