Endocrine Disease Flashcards
What is the aetiology of type 1 diabetes mellitus?
Known as insulin-dependant
Almost always seen in dogs - rare in cats.
Beta cells have been destroyed and can no longer synthesise insulin adequately.
It is presumed to be immune mediated
Predisposition in some breeds e.g. cairn, Samoyed
Damage to the pancreas may cause the inability to synthesise insulin.
What is the aetiology of Type 2 diabetes mellitus?
Usually obese cats - occasionally in dogs due to another endocrine disease or breeding cycles.
Reduced ability to respond to insulin.
Due to obesity, oestrus, Cushing’s disease, steroids, acromegaly in cats
What is the pathophysiology of diabetes mellitus?
Absolute or relative insulin deficiency
Reduced tissue utilisation of glucose
Leads to hyperglycaemia in bloodstream and low glucose levels in the cells.
Renal threshold for glucose is exceeded so get glucosuria
Eventually fats are broken down as can’t access glucose
Can lead to ketosis
What are the clinical signs of diabetes mellitus?
PUPD
Polyphagia (as not able to utilise glucose from food)
Later…
Weight loss
Signs of ketosis - vomiting, depression, dehydration
Development of cataracts (like overnight)
Describe ketoacidosis
It is an acid state in the body caused by the build up of ketones.
Gluconeogenesis occurs - when fats and proteins are used as an energy source because glucose is unavailable.
By product of this breakdown is ketones which then build up in the bloodstream causing vomiting, dehydration and anorexia
How can diabetes be diagnosed?
History and CS - very non-specific, not enough on own!
Blood tests - one on its not not indicative enough - stress can cause high blood glucose levels. Better to do a glucose curve (More info- gives image of what glucose is doing during a day). Advisable to take blood glucose sample when fasted then it shouldn’t read over 8mmol/L.
Can also do a Fructosamine test - gives average glucose over the past 2-3 weeks - external lab.Good for stressy animals.
Can also do glycosylated Hb - For longer term again monitoring. - external
Urine testing - dipsticks. Looking for presence of glucose or ketones in urine.
Ideally, we would use a combination of urine test and glucose curve in practise.
What is fructosamine?
A serum protein produced in response to blood glucose with 3 weeks lifespan
What is another name for Cushing’s disease?
Hyperadrenocorticism
What occurs in Cushing’s disease?
Blood cortisol levels are increased.
Common in middle aged to older dogs; rare in cats.
Describe the aetiology of Cushing’s disease
Can be caused by a pituitary tumour:
- it increases the production of ACTH which stimulates the adrenal gland to over-produce cortisol
Can be caused by an Adrenal tumour
- direct increase in cortisol
Both lead to increased serum levels of cortisol and the pathophysiology is related to this
Describe the pathophysiology of Cushing’s Disease
Overactive pituitary or adrenal gland leads to increased production of cortisol.
High levels of cortisol lead to hyperglycaemia (cortisol can interfere with insulin) and inhibit ADH (reducing the animal’s ability to retain water) causing PUPD.
High cortisol can also cause protein catabolism (as not able to use nutrients properly), leading to muscle wastage and poor wound healing.
Cortisol also affects hair growth and distribution of fat.
What are the clinical signs of Cushing’s Disease?
PUPD Weight loss Alopecia Pot-bellied - due to enlarged liver, abdominal fat and loss of abdominal muscle tone) Hepatomegaly Muscle weakness Panting Thinning of skin Recurrent infections and wounds that don't heal
What is the approach needed for diagnosing Cushing’s Disease?
Need to use multiple test as there is not one test that is 100% specific
What is the first choice test for diagnosing Cushing’s disease?
Low Dose Dexamethasone Suppression Test.
Give the animal a dose of dexamethasone (steroid) . In a normal dog, this increase in steroid should feedback to their pituitary gland and lower the levels of cortisol in their blood. In dogs with hyperadrenocorticism, their cortisol level will dip slightly when dex is administered but then will return to original level and not change.
Blood cortisol samples should be taken at 0,4,8 hours. Inject dex I/V after 1st blood sample.
What are the advantages and disadvantages of a Low Dose Dexamethasone Suppression Test?
Gives a good differential diagnosis. It rules out Cushing’s if the animal’s cortisol levels drop.
It requires a hospital stay which can be stressful.
