Thyroid storm, also known as thyrotoxic crisis, is a rare but life-threatening condition characterised by an extreme exacerbation of thyrotoxicosis symptoms. It occurs in approximately 1-2% of patients with established hyperthyroidism. This medical emergency demands immediate recognition and intervention because of the high mortality rate associated with it (10-30%).
Pathophysiology
Thyroid storm occurs due to a sudden and excessive release of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) into the bloodstream, overwhelming the body’s regulatory mechanisms. This hypermetabolic state dramatically increases basal metabolic rate and sympathetic nervous system activity, which can cause multi-organ dysfunction. It classically occurs in patients with underlying Graves’ disease or toxic multinodular goitre.
It is often precipitated by a physiological stressor, such as:
- Premature or inappropriate cessation of antithyroid therapy
- Recent surgery or radio-iodine treatment
- Intercurrent infection (especially chest infections)
- Trauma
- Diabetic ketoacidosis or hyperosmolar diabetic crisis
- Thyroid hormone overdose
- Pre-eclampsia
Clinical features
The clinical presentation of thyroid storm can be varied and dramatic, making early recognition challenging yet crucial.
Often, there is a sudden onset of severe hyperthyroidism with:
- Hyperpyrexia: elevated body temperature often exceeding 41°C
- Cardiovascular symptoms: heart rate greater than 140 beats per minute (with or without atrial fibrillation or other arrhythmias), hypotension, atrial dysrhythmias, congestive heart failure.
- Gastrointestinal symptoms: nausea, vomiting, diarrhoea, abdominal pain and jaundice
- Neurological symptoms: agitation, delirium, psychosis, seizures, and coma.
The hallmark of thyroid storm is the presence of these severe symptoms in conjunction with laboratory evidence of hyperthyroidism (elevated free T4 and T3, suppressed TSH).
Diagnosis and investigations
The diagnosis of thyroid storm is primarily clinical, supported by laboratory findings. Several scoring systems, such as the Burch-Wartofsky Point Scale (BWPS), help quantify the likelihood of thyroid storm based on clinical criteria. This scale considers factors such as thermoregulatory dysfunction, central nervous system effects, gastrointestinal-hepatic dysfunction, cardiovascular dysfunction, and precipitating events.
Blood tests that should be organised include:
- Full blood count
- Urea and electrolytes
- Blood glucose or bedside BM
- Coagulation screen
- CRP
- Thyroid profile (T4/T3 and TSH)
- Bone profile/calcium (10% of patients develop hypocalcaemia)
- Blood cultures
Other important investigations that should be organized include:
- Urine dipstick / MC&S
- Chest X-ray
- ECG
Management
Management of thyroid storm involves a multifaceted approach targeting the excessive thyroid hormone levels, the systemic effects of the hormone excess, and the underlying precipitating factors. Early and aggressive treatment is crucial to improving outcomes, with most patients requiring intensive care unit (ICU) admission for close monitoring and management. Key steps include:
Supportive care:
- Aggressive fluid resuscitation
- Cooling measures for hyperthermia
- Treatment of cardiac complications (e.g. beta-blockers such as propranolol or metoprolol,or calcium channel blockers such as verapamil or diltiazem for tachycardia)
Inhibition of thyroid hormone synthesis and release:
- Antithyroid medications: propylthiouracil (PTU) or methimazole to inhibit thyroid hormone synthesis
- Iodine administration: Lugol’s iodine or potassium iodide to block the release of thyroid hormones, administered after antithyroid drugs to prevent iodine from being used in new hormone synthesis
- Inhibition of peripheral conversion of T4 to T3: glucocorticoids (e.g., hydrocortisone) to reduce peripheral conversion and provide additional treatment for possible adrenal insufficiency
Treating precipitating factors:
- Any underlying causes, such as infections or discontinuation of medication, should be identified and managed
Prognosis
With timely intervention, the prognosis of thyroid storm can be significantly improved, although the condition remains associated with a high mortality rate, ranging from 10% to 30%. Long-term management includes addressing the underlying cause of hyperthyroidism to prevent recurrence and ensuring proper follow-up care.
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Thank you to the joint editorial team of www.mrcemexamprep.net for this article.
