syndrome of inappropriate ADH secretion (SIADH)

see also:

• hyponatraemia
• https://www.racgp.org.au/afp/2017/september/the-suspect-siadh/

• SIADH is increased ADH secretion despite normal or elevated plasma volume which causes reduced renal water excretion and resulting hyponatraemia and hypo-osmolality

• Barrter and Schwartz:
  • decreased serum osmolality (<275 mOsm/kg)
  • increased urine osmolality (>100 mOsm/kg)
  • euvolaemia
  • increased urine sodium (>20 mmol/L)
  • no other cause for hyponatraemia

• brain tumours
• stroke (CVA)
• subarachnoid haemorrhage (SAH)
• encephalitis
• meningitis
• encephalopathies
• brain abscess
• epilepsy
• head injury
• hydrocephalus
• psychosis
• multiple sclerosis (MS)
• cerebral lupus
• delirium tremens
• etc…

• barbiturates
• opiates and opioids
• phenothiazines
• haloperidol
• carbamazepine
• monoamine oxidase inhibitors (MAOIs)
• tricyclic antidepressants
• nicotine
• histamine
• acetylcholine
• bromocryptine
• antineoplastic agents
• chlorpropamide
• halothane
• nitrous oxide

• metformin
• tolbutamide
• griseofulvin
• aspirin (acetylsalicylic acid) and non-steroidal anti-inflammatory drugs (NSAIDs)
• theophylline
• vasopressin analogs

• ciprofloxacin
• MDMA - ecstasy
• sodium valproate (Epilim)
• SSRI/SNRI antidepressants
• many others

• most pulmonary conditions can cause it

• lung cancer
• mesothelioma
• colorectal cancer (bowel cancer)
• pancreatic cancer
• cervical cancer
• bladder cancer
• prostate cancer
• ovarian tumours
• Ewing sarcoma
• leukaemia
• lymphoma
• nasopharyngeal tumours
• thymoma
• adrenocortical carcinoma
• olfactory neuroblastoma

• small cell lung tumours
• carcinoid tumours

• exercise-induced hyponatraemia
• giant cell arteritis
• HIV / AIDS
• idiopathic

• see Mx of hyponatraemia