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Pathology
Inappropriate anti-diuretic hormone secretion leading to water retention and relative hyponatraemia.
Aetiology
Idiopathic
Endocrine: Hypothyroidism, Addison’s Disease
Ectopic Production: Small cell lung cancer, pneumonia, abscess, TB
Malignancy: Lung, pancreas, ovary, lymphoma, thymoma
CNS: Tumour, trauma, infection, strike, multiple sclerosis, Guillain-Barre
Syndrome, meningitis, encephalitis, subarachnoid haemhorrhage
Drugs: SSRIs, TCAs, opiates, haloperidol, MAOIs, diuretics, NSAIDs
Signs
Weakness, coma, euvolaemia, papilloedema, myoclonus, ataxia, tremor
Symptoms
Fatigue, confusion, falls, seizures, inappropriate thirst, headache, nausea
Investigations
Bloods: U&E – hyponatramia, serum osmolarity, TFTs and Cortisol
MSU: Urinary sodium (raised) and osmolarity
Imaging: CT head to assess for malignancy
Treatment
Fluid restriction, Demeclocycline
Prognosis
Usually good for idiopathic or drug related causes
Central pontine myelinolysis with rapid correction; to prevent this a sodium
correction rate of 0.5-1mmol/hour should be used
Key Facts
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Key References
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