Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)

Question 1

Where is ADH produced?

Answer 1

Produced by the hypothalamus and secreted by the posterior pituitary gland.

Question 2

Another name for ADH?

Answer 2

Vasopressin

Question 3

What does ADH do?

Answer 3

Stimulates water reabsorption from the collecting ducts.

Question 4

What happens to the levels of ADH in SIADH?

Answer 4

ADH is too high

Question 5

What happens to urine osmolarity in SIADH?

Answer 5

High

Question 6

What happens to blood sodium in SIADH?

Answer 6

Low

Question 7

Symptoms of SIADH?

Answer 7

Headache, fatigue, muscle aches, cramps, confusion, severe hyponatraemia (leading to seizures and reduced consciousness)

Question 8

Causes of SIADH?

Answer 8

Post-op from major surgery
Infection: atypical pneumonia, lung abscesses
Head injury
Meds: thiazide diuretics
Malignancy, esp. small cell lung cancer
Meningitis

Question 9

Can you directly measure ADH activity?

Answer 9

No

Question 10

Management of SIADH?

Answer 10

Fluid restriction: 500ml-1l
Tolvaptan (ADH receptor blocker)
Demeclocycline (tetracycline antibiotic inhibiting ADH)