SIADH Flashcards
What does SIADH stand for?
Syndrome of inappropriate antidiuretic hormone (SIADH)
What is SIADH due to?
Increased release of antidiuretic hormone (ADH) from the posterior pituitary
What does an increased release of ADH lead to?
Increased water reabsorption from the urine, diluting the blood and leading to hyponatraemia (low sodium)
Where is ADH made?
It is produced in the hypothalamus and secreted by the posterior pituitary gland
What is ADH also known as?
Vasopressin
What does vasopressin stimulate?
ADH stimulates water reabsorption from the collecting ducts in the kidneys.
What are the 2 main causes of increased ADH?
Increased secretion by the posterior pituitary
Ectopic ADH, most commonly by small cell lung cancer
What does SIADH result in?
Hyponatraemia
What are the symptoms of hyponatraemia?
Headache
Fatigue
Muscle aches and cramps
Confusion
What can severe hyponatraemia result in?
Seizures and reduced consciousness
What are the possible causes of SIADH?
Post-operative after surgery
Medications (e.g., SSRIs and carbamazepine)
Malignancy- small cell lung cancer
Brain pathologies
What medications can result in SIADH?
SSRI’s and carbamazepine
What malignancies can result in SIADH?
Small cell lung cancer
What brain pathologies can result in SIADH?
Head injury
Stroke
Intracranial haemorrhage
Meningitis
What are the main causes of SIADH?
Post-operative
SSRIs
Small cell lung cancer
What are the main clincial features of SIADH?
Euvolaemia
Hyponatraemia
Low serum osmolality
High urine sodium
High urine osmolality
What will be low in someone with SIADH?
Euvolaemia
Hyponatraemia
Low serum osmolality
What will be high in someone with SIADH?
High urine sodium
High urine osmolality
Why does correction of SIADH need to be done slowly?
Central pontine myelinolysis (osmotic demyelination syndrome)
What is the management of SIADH?
fluid restriction
demeclocycline
ADH (vasopressin) receptor antagonists
What is the function of demeclocycline?
Reduces the responsiveness of the collecting tubule cells to ADH
What is an example of a ADH (vasopressin) receptor antagonists?
Tolvaptan
