Tutorial 2 - Neurohypophysial Disorders Flashcards
(16 cards)
CASE 1
Mrs. X
43 years old
Mother of two children
Sent to the endocrine clinic at Charing Cross Hospital by her GP
Presenting Complaint/History of PC/Examination
- complaining of always being thirsty
- it was disrupting her sleep so that she was permanently tired.
Blood results
- fasting blood sample = 5.3 mmol/l
- thyroid function tests = normal
- plasma osmolality = 295 mOsm/kg H2O
- plasma Na+ concentration = 146 mmol/l
Water Deprivation Test
- body weight was measured before the urine sample collection on each occasion
- the clinical staff carrying out the test were told to stop the test if the patient lost more than 3% of her body weight
What is the normal plasma osmolality range?
[CASE 1]
275-295 mOsm/kg H2O
What is the normal plasma sodium range?
[CASE 1]
135-145 mmol/l
What evidence from the initial blood sample analysis might have suggested diabetes mellitus or primary hypothyroidism?
[CASE 1]
Fasting Blood Glucose
- >7mmol/L
- suggests diabetes mellitus
T4/TSH Test
- low T4
- high TSH
- suggest primary hypothyroidism
Explain the physiological basis for the water deprivation test.
[CASE 1]
H20 deprivation would result in a rise in plasma osmolality
This stimulates ADH release
This goes to the kidneys which causes fluid reabsorption in the collecting ducts
This concentrates urine
Can see if ADH is working
Why should the test be stopped if the patient loses > 3% of her body weight?
[CASE 1]
Because this is a marker of signs of dehydration
This may happen in H2O deprivation test in diabetes insipidus
What is the diagnosis?
[CASE 1]
Diabetes Insipidus
How do the results after DDAVP administration identify the precise nature of the disorder?
[CASE 1]
She has Central (Cranial) Diabetes Insipidus
We know this because she responded to DDAVP and concentrated her urine volume
Nephrogenic DI would have no response to DDAVP because there is a problem with the V2 receptors and the maximum would be a very small response
How should this patient be treated?
[CASE 1]
Nasal DDAVP Spray
It is specific to V2 receptors
V2 receptor agonist
CASE 2
Mr. N
Presenting Complaint/History of PC/Examination
- treated for a lung tumour by radiotherapy
- second radiotherapy session at hospital, he reported feeling unwell
- specifically feeling confused and unsteady
Blood Results
- Serum [Na+] = 126 mmol/L
- Plasma osmolality = 270 mOsm/kg H2O
What is the normal range for serum [Na+]?
[CASE 2]
133-146 mmol/L
What could be the cause for the feeling of confusion and unsteadiness?
Hyponatraemia
Low Na+ affects CNS function
What is the diagnosis?
[CASE 2]
SIADH (Syndrome of Inapproparite ADH)
This has occurred because of the lung tumour
Tumours often produce random hormones such as ectopic ADH
Typically small cell lung tumours
Which hormone could be involved, and what could its source be?
[CASE 2]
ADH (Vasopressin)
Possible source is the lung tumour releasing ectopic ADH
It’s made in excessive quanitites causing excessive H2O reabsorption meaning that the blood is diluted
This causes the hyponatraemia
What would be the appropriate treatment for these symptoms in Mr. N?
[CASE 2]
- Surgery or something else to treat the lung tumour
- Then fluid restriction [500ml-1500ml] unless <110 for Na+
- If fluid restriction doesn’t work, demecylocline makes kidneys more resistant and gives the effect of nephrogenic DI. It is not permanent and has to be stopped after a time.
- Vaptans, bind to V2 receptors so that ADH can’t bind
If Na+ was really low
- give Na+ through hypertonic saline (3%)
How much more likely are females to develop autoimmune diseases than males?
10x more likely
