Neurohypophysial disorders Flashcards
Which part of the pituitary gland is more likely to be cancerous?
Anterior Pituitary
What are the hormones produced by the Neurohypothesis? What do they do?
Vasopression/ADH V2 receptors in collecting duct-increasing AQPR2 and uptake water
Oxytocin-useless shit
What regulates Vasopressin release?
Osmoreceptors (neurones)-in Organum Vasculosum (near hypothallamus) and they signal to hypothallamus
In details, Sensitive osmoreceptors detect changes. As Na+ increase, shrink of osmoR (water comes out)-fire, triggers vasopressin from PVN and SON neurons
What is the physiological response to water deprivation?
As you have low water-increase serum osmolarity-firing of osmoreceptors-release of vasopressin->increase water reabsobtion -> Less urine/Higher urine conc
-> Lower Serum Conc
Also would activate thirst
What is the name of the disease in which you have insufficient ADH? What are the 2 types, and which one is the most common?
Diabetes insipidus type 1 and 2
Type 1-lack of ADH (Cranial/Central), type 2-bad working/resistance of ADH receptors (Nephrogenic)
Type 1 is more common
What is the aetiology of Cranial DI?
More common-and aquired
(After TBI, Pit surgery, Pit tumours (damage), Metastasis to the Pit, Granulomous infiltration of median eminance (TB, sarcoidis)
Can be congenital
What is the aetiology of nephrogenic DI?
Congernital (rare)-mutation of V2, AQPR2, etc)
Aquired (rarer)-Drugs (usually lithium based)
What are the signs and symptoms of DI?
Polyuria (but HYPOTONIC urine-dilute), Polydypsia,
Dehydration (and consequences)-can lead to death if no water to drink
Disruption to sleep
Increased plasma Osmolarity (like sodium )
What is a disease with similar symptoms to DI, but not related?
Psychogenic Polydipsia-no ADH issue
But they drink all the time
Can be in psycological patients, sometimes drugs (dry mouth sensation), can be because of “drink plenty” recomendation) => will lead to large urine volumes (but not abnormal)
What is the main testable difference bewteen DI and psychogenuc Polydipsia? What is the main test used-describe it?
DI patients have overly high plasma Osmolarity (cause dehydrated)
PP patiens have low plasma Osm (because drink so much)
The Water deprivation test can easily show the difference
-When normally hydrated-normal diluted urine
When Fluid deprived-normal high Osm urine and have very little (cause no drinking). Some one with PP-pretty much same as normal, just bit lower Osm (have more water in them). Some one with DI, Plasma OSM will still be low (very) and will be passing large amounts of urine
To seperate between the two types of DI, DDAVP is given (vasopressin analogue)-Central DI Urine OSM increase, Nephrogenic no change
Why is it important to measure body weight during a Water deprivation test?
in DI patients, where they need to drink a lot to live, if they lose over 3% of their body weight-dehydrated and need to stop
What are the main biochemical features of DI?
No glucose in urine
HypERnatreamia, Raised Urea, increased plasma osmolality, dilute (hypo-osmolar) urie
What are the main biochemical features of Psychogenic polydypsia?
Mild Hyponatreamia, low plasma osm, dilute urine
How do you treat cranial DI? How can it be administered?
Need a V2 specific receptor to not cause vasodilation and similar-Desmopressin (DDAVP)
Usually nasally-which means can be lost on the way to hospital. Can be orally and SC
But also careful, because if they drink the same amount of water-hyponatreamia
How do you treat nephorgenic DI?
Cannot use desmopressin
Some people use Thiazides (even if diuretics? lectured unsure?
