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BRS2 Endocrinology > Disorders of Vasopressin > Flashcards

Disorders of Vasopressin Flashcards

1
Q

Which structure is posterior pituitary anatomically continuous with?

A

Hypothalamus

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2
Q

What are the neurons containing AVP called?

A

Hypothalamic magnocellular neurons

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3
Q

What is diuresis?

A

Production of urine

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4
Q

What is the main physiological action of AVP?

A

Stimulation of water reabsoprtion in the renal collecting duct, resulting in concentrated urine

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5
Q

Which receptor does AVP act on to reabsorb water?

A

V2 receptor

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6
Q

What is the secondary physiological action of AVP?

A

Vasoconstriction

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7
Q

Which receptor does AVP act on to vasoconstrict?

A

V1 receptor

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8
Q

Release of which hormone from anterior pituitary is stimulated by AVP?

A

ACTH

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9
Q

What type of receptor is V2 receptor?

A

G protein-coupled receptor (GPCR)

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10
Q

What is the action mechanism of AVP?

A
  1. Binds to V2 receptor on the basolateral membrane
  2. Signalling cascade via cAMP to insert aquaporin-2 channels on the apical membrane
  3. Water moves in to the collecting duct cell by osmosis through AP-2
  4. Water moves out of the cell through AP-3 channels and into the bloodstream
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11
Q

What is osmolality?

A

Concentration relative to the mass of solvent

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12
Q

What stimulates AVP release?

A

Increase in plasma osmolality

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13
Q

What are the sensory receptors specialised to detect changes in plasma osmolality called?

A

Osmoreceptors

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14
Q

What is the action mechanism of osmoreceptors?

A
  1. Increase in plasma ion concentration
  2. Water moves out of osmoreceptor causing it to shrink
  3. Increased osmoreceptor firing triggering AVP release
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15
Q

What sensation do osmoreceptors cause when plasma osmolality is high?

A

Thirst

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16
Q

What are the 2 main AVP disorders?

A
  • Arginine Vasopressin Deficiency (AVP-D)
  • Arginine Vasopressin Resistance (AVP-R)
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17
Q

What is AVP-D also known as?

A

Cranial Diabetes Insipidus (CDI)

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18
Q

What is AVP-R also known as?

A

Nephrogenic Diabetes Insipidus

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19
Q

What is the medical term used to describe excessive thirst?

A

Polydipsia

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20
Q

What is the result of long-term dehydration of a diabetes insipidus patient?

A

Death

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21
Q

What is polyuria?

A

Excessive passing of urine

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22
Q

What is nocturia?

A

Waking up at night to pass urine

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23
Q

What is polydipsia?

A

Excessive thirst

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24
Q

What are the symptoms of AVP-D/AVP-R?

A
  • Polyuria
  • Nocturia
  • Polydipsia
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25
Q

What is the underlying cause of AVP-D?

A

Unable to make or secrete AVP (problem with hypothalamus or posterior pituitary)

26
Q

What is the underlying cause of AVP-R?

A

Collecting duct unable to respond to AVP (normal hypothalamus and poaterior pituitary)

27
Q

What is the most common cause of polyuria, nocturia and polydipsia?

A

Diabetes mellitus

28
Q

Why does diabetes mellitus cause polydipsia and polyuria?

A

Hyperglycaemia results in osmotic diuresis

29
Q

What is osmotic diuresis?

A

Increased amount of solutes in renal tubules drawing more water into the urine

30
Q

Which type of AVP disorder is more common?

A

AVP-D

31
Q

Which type of AVP-D is more common?

A

Acquired

32
Q

Which type of AVP-R is more common?

A

Acquired

33
Q

What are the causes of acquired AVP-D?

A
  • Traumatic brain injury
  • Pituitary surgery
  • Pituitary tumour
  • Inflammation of pituitary stalk (e.g. TB)
  • Autoimmune
34
Q

What are the causes of congenital AVP-R?

A
  • Mutation in V2 receptor gene
  • Mutation in AP-2 channel gene
35
Q

What is a common cause of acquired AVP-R?

A

Drugs (e.g. lithium)

36
Q

How is the urine concentration described in diabetes insipidus?

A

hypo-osmolar (dilute) urine

37
Q

How is the plasma concentration described in diabetes insipidus?

A

hyper-osmolar plasma

38
Q

How is the plasma sodium concentration described in diabetes insipidus?

A

Hypernatraemia

39
Q

How is the plasma glucose concentration described in diabetes insipidus?

A

Normal

40
Q

What can mimic AVP disorder except for diabetes mellitus?

A

Pyschogenic Polydipsia

41
Q

What causes the symptoms in pyschogenic polydipsia?

A

Patient drinking excessive water

42
Q

How do we distinguish between pyschogenic polydipisa and AVP disorder?

A

Water deprivation test

43
Q

What is measured over time in water deprivation test?

A
  • Urine volume
  • Urine osmolality
  • Plasmaa osmolality
44
Q

What is checked regulary to ensure patient safety during water deprivation test?

A

Weight

45
Q

What is the marker of significant dehydration in a water deprivation test?

A

Loss of more than 3% body weight

46
Q

Pyschogenic polydipsia, AVP deficiency/resistance and normal are represented by which lines?

A
47
Q

What is used during water deprivation test to distinguish between AVP-D and AVP-R?

A

Administration of desmopressin

48
Q

What does desmopressin mimic?

A

AVP

49
Q

What is the physiological response to desmopressin for AVP-D?

A

Increased urine osmolality

50
Q

What is the physiological response to desmopressin for AVP-R?

A

No change in urine osmolality

51
Q

AVP-D and AVP-R are represented by which lines?

A
52
Q

Which AVP receptor is desmopressin selective for and which one it is not?

A

Selective for V2 (not selective for V1)

53
Q

What is the treatment for AVP-D?

A

Desmopressin

54
Q

What are the 2 forms desmopressin is available in?

A
  1. Intranasal
  2. Oral tablet
55
Q

What is name of the disorder associated with excess AVP production?

A

Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)

56
Q

How are the urine, plasma and plasma sodium concentrations affected in SIADH?

A

High urine osmolality
Low plasma osmolality
Hyponatraemia

57
Q

What are the causes of SIADH?

A
  • Head injury, stroke tumour
  • Pneumonia
  • Small cell lung cancer
  • Anti-epileptic, anti-depresseant
  • Idiopathic
58
Q

How is SIADH managed?

A

Fluid restriction

59
Q

Which drug can be administered for SIADH patients?

A

Vaptan

60
Q

What is vaptan?

A

Vasopressin receptor antagonist

BRS2 Endocrinology (3 decks)

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