Presents as an exacerbation of the clinical features of hyperthyroidism (e.g. pyrexia, hyperdynamic circulation, heart failure, confusion). There is usually a precipitating factor such as infection, surgery, ketoacidosis, myocardial infarction or childbirth. It may present with exhaustion in the elderly with few features of hyperthyroidism. The diagnosis is confirmed by standard thyroid function tests.
• Pyrexia should be controlled by surface cooling (avoid aspirin which displaces thyroxine from plasma proteins).
• Catecholamine effects should be reduced by p blockade (e.g. propranolol 1-5 mg IV then 20-80 mg qds PO). These should be used with caution if there is acute heart failure.
• Blockade of thyroxine synthesis is achieved by potassium iodide 200-600 mg IV over 2 h then 2 g/day PO and carbimazole 60-120 mg/day PO.
• Blockade of peripheral T4 to T3 conversion is achieved by dexamethasone 2 mg qds IV.
• Careful fluid and electrolyte management is essential.
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