anti-diuretic hormone disorders

Question 1

diabetes insipidus response vs normal person

Answer 1

diabetes insipidus - excess dilute urine - extreme thirst

normal person:
- hypothalamus produces vasopressin (ADH) - stored in pituitary glands
- ADH released when water in body is too low
- ADH retains water by reducing amount lost via kidneys
RESPONSE = MORE CONC. URINE

diabetes insipidus
- reduced production of ADH
- kidneys don’t retain as much water
- too much water passed from body
- causes thirst/polyuria
RESPONSE = MORE DILUTE URINE

Question 2

types of diabetes insipidus and treatment

Answer 2

pituitary (cranial)
- lack of ADH production (most common type)
- treatment: vasopressin or desmopressin

nephrogenic (partial)
- kidneys do not respond to ADH
- treatment: thiazide diuretic (paradoxical effect) - helps retain

Question 3

excess ADH treatment

Answer 3

excess ADH - body stores too much water - dilutes salt conc. in blood - hyponatraemia

treatment: treats hyponatremia
1 - fluid restriction
2 - demeclocycline (tetracycline - blocks renal tubular effects of ADH)
3 - tolvaptan (vasopressin antagonist)

avoid rapid correction of hyponatraemia with tolvaptan - osmotic dyemyelination - serious neurological effects

Question 4

desmopressin imp points

Answer 4

more potent + longer duration of action compared to vasopressin

c/i - history of hyponatremia, diuretic use, > 65 (increased risk of hyponatremia + renal impairment)

fluid retention + hyponatremia - nausea, headache, convulsions

advise person to limit fluid intake 1 hour before and 8 hrs after dose

interactions - SSRI, carbamzepine, diuretics - hyponatremia