ANTIDIURETIC HORMONE DISORDERS Flashcards
Diabetes insipidus
Excess dilute urine = extreme thirst
What is ADH?
Antidiuretic Hormone, also known as vasopressin
Where is ADH produced and stored
Hypothalamus
Pituitary gland
Primary function of ADH
Regulates water balance in the body by controlling the amount of water the kidney reabsorbs
ADH production (normal)
- Hypothalamus produces vasopressin (ADH)
- stored in pituitary gland - ADH released when water in the body is too low (dehydration)
- ADH retains water in the body by reducing amount of water lost through kidneys
more CONC urine
ADH production (DI)
- Reduced production of ADH
- Kidneys do not retain as much water
- Too much water passed from body
- Causes extreme thirst/polyuria
more DILUTE urine
Urine output in person with DI
Consistently high
Frequent urination
Dehydration
What are the 2 types of DI?
Pituitary (cranial)
Nephrogenic (partial)
What is the difference between nephrogenic and cranial Diabetes insipidus
Cranial means that the pituitary produces less ADH
Nephrogenic means that the kidneys are resistant to effects of ADH (no water retention)
Pituitary (cranial) DI
Lack of vasopressin (ADH) production
Most common type
Treatment of pituitary (cranial) DI
Vasopressin or desmopressin
Nephrogenic (partial) DI
Kidneys do not respond to ADH
Nephrogenic (partial) treatment
Thiazide diuretic
Paradoxical effect - you would expect this to make pt urinate more. but in this instance it has the opposite effect
General MoA of thiazide diuretics
- Increase urine production = helps body get rid of excess salt and water
- Act on kidney, specifically distal convoluted tubule to reduce reabsorption of sodium and water = increased urine output
Thiazide diuretic
Paradoxical effect
- Enhance the reabsorption of sodium and water in the kidneys
- Indirectly reduces the amount of urine produced
- This concentrates the urine and decrease the volume of urine output
Desmopressin
- More potent
- Longer duration of action than vasopressin
- No vasoconstrictor effect
Desmopressin - how to take
Limit fluid intake 1 hour before dose and until 8 hours after
Desmopressin - SEs
- Hyponatraemia
- Nausea
This AED drug may be useful sometimes in partial pituitary diabetes insidious (unlicensed)
Carbamazepine
- Sensitising renal tubules to action of vasopressin
Increased ADH
- Body stores too much water
- Dilutes the salt conc in the blood
- Hyponatraemia
Drugs which increase vasopressin secretion
Paracetamol
Nicotine
TCAs
What is hyponatraemia
Low sodium level in the blood
Hyponatraemia in elderly
Increased risk of hyponatraemic convulsions
Measure baseline Na
Monitor regularly; discontinue if levels fall below baseline
Treatment of hyponatraemia
- Fluid restriction
- Demeclocycline
- Tolvaptan
Demeclocycline
blocks renal tubular effect of ADH
Tolvaptan
vasopressin antagonist
How to AVOID rapid correction of hyponatraemia with tolvaptan
Causes osmotic demyelination → serious neurological events
