Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

*Y2 LCRS Endo* > Neurohypophysial Disorders > Flashcards

Neurohypophysial Disorders Flashcards

1
Q

Where are the Osmoreceptors that regulate Vasopressin Release Located?

A

Organum Vasculosum; neurones located here project to Hypothalamus Paraventricular and Supraoptic nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does an Osmoreceptor work?

A

Very sensitive to changes in osmolality of ECF.

Increase in EC Na+ (during dehydration) causes osmosis of water out of osmoreceptor neurone.

Cells shrink which causes excitation and increased firing of neurone

Leads to increased production of VP from PP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define osmolality:

A

The concentration of all solutes in a given weight of water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the sequence of events that occurs when you are water-deprived:

A
  1. Increased serum osmolality
  2. Stimulation of osmoreceptors
  3. Thirst/Increased VP release
  4. Increased water reabsorption from Renal collecting ducts
  5. Reduction in urine volume/serum osmolality
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a basic definition of Diabetes Insipidus?

A

When there is insufficient ADH, or ADH doesn’t work, leading to chronic polydipsia and dehydration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of Diabetes Insipidus, and what characterises them?

A

Cranial (central) - Absence or lack of circulating vasopressin

Nephrogenic - End organ (kidney) resistance to vasopressin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the Aetiology of Cranial DI?

3 ways from most to least common:

A

Acquired

Damage to neurohypophysial system

Congenital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What types of damage to the Neurohypophysial system can cause Cranial DI?

A
  • Traumatic brain injury
  • Pituitary surgery
  • Pituitary tumours, craniopharyngioma
  • Metastasis to the pituitary gland eg breast
  • Granulomatous infiltration of median eminence eg TB, sarcoidosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the aetiologies of Nephrogenic DI?

A

Acquired - via drugs like Lithium

Congenital - mutation in V2 receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the signs and symptoms of DI?

A

Polyuria

Hypo-osmolar urine (Dilute)

Polydipsia

Dehydration

Disruption to sleep from symptoms (nocturia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe what happens during dehydration in patients with DI?

A

Increased firing of Osmoreceptors, but no ADH increase/release

Continued production of large volumes of dilute urine

Increase in plasma osmolality

Reduction in EC fluid volume

Thirst still present so drinking

EC fluid volume expansion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is Psychogenic Polydipsia?

A

Excess water intake - excess urine output

Usually in psychiatric patients, possibly due to dry-mouth side effect.

Can be bc of medical advice to drink plenty of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe what happens upon increased drinking in patients with Psychogenic Polydipsia

A

The normal homeostatic mechanism

ADH functions correctly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the normal range for Plasma Osmolality?

A

270-290 mOsm/kg H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What can be diagnosed when Plasma Osmolality is above the normal range?

A

Diabetes insipidus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can be diagnosed when Plasma Osmolality is below the normal range?

A

Psychogenic polydipsia

17
Q

Describe a Water Deprivation Test:

A

Patient not given water, mass constantly measured

Urine osmolality measured to see response to water deprivation

DDAVP administered at the end to see response to artificial vasopressin

18
Q

Describe what you would you see on a Water Deprivation test in patients with DI, P Polydispia and Normal Patients

A

In normal and P Polydipsia patients, urine osmolality increases as normal, but in DI patients, osmolality remains low.

When DDAVP administered, cranial DI patients will begin to retain water and Urine osmolality will increase

19
Q

What is the marker of clinical dehydration?

A

A 3% loss of bodymass upon fluid deprivation.

Stop test then and give DDAVP or water

20
Q

How do you differentiate between Central and Nephrogenic DI in a Water deprivation test?

A

DDAVP will cause an increase in Urine osmolality in cranial DI patients, but not nephrogenic, as they are insensitive to VP

21
Q

When should you suspect DI?

A

Polyuria

Polydipsia

ONE . MORE

These symptoms suggest Diabetes Mellitus which is much more common and should be investigated first.

22
Q

What are the biochemical features of DI?

A
  • Hypernatraemia
  • Raised urea
  • Increased plasma osmolality
  • Dilute (hypo-osmolar) urine - ie low urine osmolality
23
Q

What are the biochemical features of Psychogenic Polydipsia?

A
  • Mild hyponatraemia – excess water intake
  • Low plasma osmolality
  • Dilute (hypo-osmolar) urine - ie low urine osmolality
24
Q

How is Central DI treated?

A

Desmopressin (DDAVP) given

It is a V2 specific agonist

25
Q

How can Desmopressin be administered?

A

Nasal spray (could be mistaken for unimportant medicine)

Can be given orally

26
Q

What should you tell a patient who is starting Desmopressin?

A

Patients must be told not to continue to drink large volumes of water, or they risk Hyponatraemia

27
Q

How do you treat Nephrogenic DI?

A

Thiazides

28
Q

What does SIADH stand for?

A

Syndrome of inappropriate ADH

29
Q

Define what SIADH is:

A

“the plasma vasopressin concentration is inappropriately high for the existing plasma osmolality”

30
Q

What are the possible signs of SIADH?

A

Raised Urine Osmolality

Decreased urine volume

Hyponatraemia

31
Q

What are the possible symptoms of SIADH?

A

Can be asymptomatic

If p[Na+] <120 mM; weakness, poor mental function and nausea

If p[Na+] <110 mM; Confusion leading to Coma and ultimately death

32
Q

What are the possible causes of SIADH

A

Often idiopathic, otherwise:

•CNS

–SAH, stroke, tumour, TBI

•Pulmonary disease

–Pneumonia, bronchiectasis

•Malignancy

–Lung (small cell)

•Drug-related

–Carbamazepine, SSRI

33
Q

What is the normal treatment of SIADH?

A

Immediate fluid restriction

Appropriate treatment for cause, e.g. surgery for tumour excision

Demeclocycline to induce nephrogenic DI

34
Q

What drugs can be given to treat SIADH and how does this work?

A

Vaptans: non-competitive V2 receptor antagonists.

Very expensive, rarely used

Inhibit AQP2 synthesis - aquaresis - solute sparing excretion of water

*Y2 LCRS Endo* (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions