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BRS2 Endocrinology > Disorders of Vasopressin > Flashcards

Disorders of Vasopressin Flashcards

(60 cards)

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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
What is the underlying cause of AVP-D?
Unable to make or secrete AVP (problem with hypothalamus or posterior pituitary)
26
What is the underlying cause of AVP-R?
Collecting duct unable to respond to AVP (normal hypothalamus and poaterior pituitary)
27
What is the most common cause of polyuria, nocturia and polydipsia?
Diabetes mellitus
28
Why does diabetes mellitus cause polydipsia and polyuria?
Hyperglycaemia results in osmotic diuresis
29
What is osmotic diuresis?
Increased amount of solutes in renal tubules drawing more water into the urine
30
Which type of AVP disorder is more common?
AVP-D
31
Which type of AVP-D is more common?
Acquired
32
Which type of AVP-R is more common?
Acquired
33
What are the causes of acquired AVP-D?
* Traumatic brain injury * Pituitary surgery * Pituitary tumour * Inflammation of pituitary stalk (e.g. TB) * Autoimmune
34
What are the causes of congenital AVP-R?
* Mutation in V2 receptor gene * Mutation in AP-2 channel gene
35
What is a common cause of acquired AVP-R?
Drugs (e.g. lithium)
36
How is the urine concentration described in diabetes insipidus?
hypo-osmolar (dilute) urine
37
How is the plasma concentration described in diabetes insipidus?
hyper-osmolar plasma
38
How is the plasma sodium concentration described in diabetes insipidus?
Hypernatraemia
39
How is the plasma glucose concentration described in diabetes insipidus?
Normal
40
What can mimic AVP disorder except for diabetes mellitus?
Pyschogenic Polydipsia
41
What causes the symptoms in pyschogenic polydipsia?
Patient drinking excessive water
42
How do we distinguish between pyschogenic polydipisa and AVP disorder?
Water deprivation test
43
What is measured over time in water deprivation test?
* Urine volume * Urine osmolality * Plasmaa osmolality
44
What is checked regulary to ensure patient safety during water deprivation test?
Weight
45
What is the marker of significant dehydration in a water deprivation test?
Loss of more than 3% body weight
46
Pyschogenic polydipsia, AVP deficiency/resistance and normal are represented by which lines?
47
What is used during water deprivation test to distinguish between AVP-D and AVP-R?
Administration of desmopressin
48
What does desmopressin mimic?
AVP
49
What is the physiological response to desmopressin for AVP-D?
Increased urine osmolality
50
What is the physiological response to desmopressin for AVP-R?
No change in urine osmolality
51
AVP-D and AVP-R are represented by which lines?
52
Which AVP receptor is desmopressin selective for and which one it is not?
Selective for V2 (not selective for V1)
53
What is the treatment for AVP-D?
Desmopressin
54
What are the 2 forms desmopressin is available in?
1. Intranasal 2. Oral tablet
55
What is name of the disorder associated with excess AVP production?
Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)
56
How are the urine, plasma and plasma sodium concentrations affected in SIADH?
High urine osmolality Low plasma osmolality Hyponatraemia
57
What are the causes of SIADH?
* Head injury, stroke tumour * Pneumonia * Small cell lung cancer * Anti-epileptic, anti-depresseant * Idiopathic
58
How is SIADH managed?
Fluid restriction
59
Which drug can be administered for SIADH patients?
Vaptan
60
What is vaptan?
Vasopressin receptor antagonist

BRS2 Endocrinology (3 decks)

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