Endocrine II Flashcards
What are the three disorders of the pituitary-adrenal axis?
- Hypoadrenocorticism of the dog
- Hypersomatotropism
- (pituitary pars intermedia dysfunction
What can cause hypercortisolaemia?
Usually spontaneous conditions
* Pituitary dependent hyperadrenocorticism
* Functional adrenocortical neoplasia
* Stress Induced hypercortisolaemia
What is an iatrogenic way that an animal can get Hypercortisolaemia?
administration of exogenous ACTH
How does stress induced hypercortisolaemia occur?
- Illness or other stress can stimulate release of CRH
- CRH stimulates more production of ACTH
- ACTH acts on adrenal glands to stimulate increased production of cortisol
- If stress is persistent you may get bilateral adrenalcortical hyperplasia
What are the key facts surrounding hyperadrenocorticism?
- It is an excess production of cortisol
- The majority of cases in canines and felines are due to a pituitary adenoma
How does a pituitary tumour effect the adrenal glands?
Causes an increase in ACTH, this stimulates an increased cortisol production by the adrenal glands
What effect does an adrenal tumour have?
Increased production of cortisol (this is not responsive in any way to supression)
How may you diagnose hypoadrenocorticism in a laboratory assesment?
- The secretion of ACTH an/ or cortisol is often pulsatile so you cannot do a basal sample
- dynamic tests have to be used for diagnostic purposes
What is the potential issue with colecting ACTH in-vitro?
It is said to be labile (breaks down easily) and therefore it can be hard to obtain a required sample
What is a common laboratory change?
A ‘stress leukogram’ which is made up of
* leukocytosis
* neutrophillia
* lymphopaenia
* low eosinophils
Increased lipids, increased glucose,
Urine is likely to be relatively unconcentrated
What are the four tests you can do to test for hyperadrenocorticism?
- UCCR
- LDDST
- ACTH
- HDDST
How does UCCR work?
Compare the creatinine that is freely filtered through the kidney to another solute
Collect a urine sample and send it for lab testing to compare creatinine and cortisol levels
What is the meaning of the UCCR results
an increase in the ratio means an increased cortisol excretion in the urine and therefore increased cortisol in the blood
The test is highly sensitive
and usually used for screening only
How does a LDDST test work?
- take the basal cortisol level
- administer dexamethasone (limited cross-reactivity)
- dexamethasone has the same effect on adrenal glands as cortisol
How does an ACTH stimulation test work?
administer a high amount of ACTH to obtain a maximal release of cortisol from the adrenal glands
How does a HDDST test work?
administration of a dose of corticosteroid should suppress
endogenous cortisol production due to the negative feedback pathways
Why do we need to differentiate between PDH and ADH?
If its a unilateral adrenal mass we can then do surgery to remove it (this may not be straightforward if its an adenocarcinoma)
In approximately how many feline DM patients is Hypersomatotropism also present?
around 15-25%
How can you diagnose acromegaly (increase in GH)
IGF-1 appears to mirror GH well
so any increase in IGF-1 can be used as a diagnosis for hypersomatotropism
What is the treatment for Feline Hypersomatotropism?
Both medical and surgical options are available
but cost is an issue for both options
What is PPID?
Neoplasia of the pituitary pars intermedia
causes increased secretion of ACTH
How may you diagnose PPID?
- Measurement of ACTH
- TRH stimulation test- measuring ACTH
