ANTIDIURETIC HORMONE DISORDERS Flashcards

1
Q

Diabetes insipidus

A

Excess dilute urine = extreme thirst

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2
Q

What is ADH?

A

Antidiuretic Hormone, also known as vasopressin

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3
Q

Where is ADH produced and stored

A

Hypothalamus
Pituitary gland

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4
Q

Primary function of ADH

A

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

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5
Q

ADH production (normal)

A
  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

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6
Q

ADH production (DI)

A
  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

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7
Q

Urine output in person with DI

A

Consistently high
Frequent urination
Dehydration

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8
Q

What are the 2 types of DI?

A

Pituitary (cranial)
Nephrogenic (partial)

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9
Q

What is the difference between nephrogenic and cranial Diabetes insipidus

A

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

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10
Q

Pituitary (cranial) DI

A

Lack of vasopressin (ADH) production
Most common type

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11
Q

Treatment of pituitary (cranial) DI

A

Vasopressin or desmopressin

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12
Q

Nephrogenic (partial) DI

A

Kidneys do not respond to ADH

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13
Q

Nephrogenic (partial) treatment

A

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

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14
Q

General MoA of thiazide diuretics

A
  • 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
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15
Q

Thiazide diuretic
Paradoxical effect

A
  • 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
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16
Q

Desmopressin

A
  • More potent
  • Longer duration of action than vasopressin
  • No vasoconstrictor effect
17
Q

Desmopressin - how to take

A

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

18
Q

Desmopressin - SEs

A
  • Hyponatraemia
  • Nausea
19
Q

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

A

Carbamazepine
- Sensitising renal tubules to action of vasopressin

20
Q

Increased ADH

A
  • Body stores too much water
  • Dilutes the salt conc in the blood
  • Hyponatraemia
21
Q

Drugs which increase vasopressin secretion

A

Paracetamol
Nicotine
TCAs

22
Q

What is hyponatraemia

A

Low sodium level in the blood

23
Q

Hyponatraemia in elderly

A

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

24
Q

Treatment of hyponatraemia

A
  1. Fluid restriction
  2. Demeclocycline
  3. Tolvaptan
25
Q

Demeclocycline

A

blocks renal tubular effect of ADH

26
Q

Tolvaptan

A

vasopressin antagonist

27
Q

How to AVOID rapid correction of hyponatraemia with tolvaptan

A

Causes osmotic demyelination → serious neurological events