ANTIDIURETIC HORMONE DISORDERS

Question 1

Diabetes insipidus

Answer 1

Excess dilute urine = extreme thirst

Question 2

What is ADH?

Answer 2

Antidiuretic Hormone, also known as vasopressin

Question 3

Where is ADH produced and stored

Answer 3

Hypothalamus
Pituitary gland

Question 4

Primary function of ADH

Answer 4

Regulates water balance in the body by controlling the amount of water the kidney reabsorbs

Question 5

ADH production (normal)

Answer 5

1. Hypothalamus produces vasopressin (ADH)
   - stored in pituitary gland
2. ADH released when water in the body is too low (dehydration)
3. ADH retains water in the body by reducing amount of water lost through kidneys

more CONC urine

Question 6

ADH production (DI)

Answer 6

1. Reduced production of ADH
2. Kidneys do not retain as much water
3. Too much water passed from body
4. Causes extreme thirst/polyuria

more DILUTE urine

Question 7

Urine output in person with DI

Answer 7

Consistently high
Frequent urination
Dehydration

Question 8

What are the 2 types of DI?

Answer 8

Pituitary (cranial)
Nephrogenic (partial)

Question 9

What is the difference between nephrogenic and cranial Diabetes insipidus

Answer 9

Cranial means that the pituitary produces less ADH
Nephrogenic means that the kidneys are resistant to effects of ADH (no water retention)

Question 10

Pituitary (cranial) DI

Answer 10

Lack of vasopressin (ADH) production
Most common type

Question 11

Treatment of pituitary (cranial) DI

Answer 11

Vasopressin or desmopressin

Question 12

Nephrogenic (partial) DI

Answer 12

Kidneys do not respond to ADH

Question 13

Nephrogenic (partial) treatment

Answer 13

Thiazide diuretic
Paradoxical effect - you would expect this to make pt urinate more. but in this instance it has the opposite effect

Question 14

General MoA of thiazide diuretics

Answer 14

• 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

Question 15

Thiazide diuretic
Paradoxical effect

Answer 15

• 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

Question 16

Desmopressin

Answer 16

• More potent
• Longer duration of action than vasopressin
• No vasoconstrictor effect

Question 17

Desmopressin - how to take

Answer 17

Limit fluid intake 1 hour before dose and until 8 hours after

Question 18

Desmopressin - SEs

Answer 18

• Hyponatraemia
• Nausea

Question 19

This AED drug may be useful sometimes in partial pituitary diabetes insidious (unlicensed)

Answer 19

Carbamazepine
- Sensitising renal tubules to action of vasopressin

Question 20

Increased ADH

Answer 20

• Body stores too much water
• Dilutes the salt conc in the blood
• Hyponatraemia

Question 21

Drugs which increase vasopressin secretion

Answer 21

Paracetamol
Nicotine
TCAs

Question 22

What is hyponatraemia

Answer 22

Low sodium level in the blood

Question 23

Hyponatraemia in elderly

Answer 23

Increased risk of hyponatraemic convulsions
Measure baseline Na
Monitor regularly; discontinue if levels fall below baseline

Question 24

Treatment of hyponatraemia

Answer 24

1. Fluid restriction
2. Demeclocycline
3. Tolvaptan

Question 25

Demeclocycline

Answer 25

blocks renal tubular effect of ADH

Question 26

Tolvaptan

Answer 26

vasopressin antagonist

Question 27

How to AVOID rapid correction of hyponatraemia with tolvaptan

Answer 27

Causes osmotic demyelination → serious neurological events