Hypoadrenocorticism Flashcards
What is the definition of hypoadrenocorticism?
Disorder resulting in marked adrenocorticolysis, usually immune mediated
Results in reduced capacity to produce…
Cortisol and aldosterone
Is it always clinically significant?
no, some not clin sig
Do all cases have electrolyte disturbances?
No, non-typical hypoA has no electrolyte disturbances
what is critical illness related corticosteroid insufficiency? (CIRCI)
Critically ill animals which are unable to produce adequate cortisol to deal with their illness. Can’t therefore recover from their illness
What is typical hypoadrenocorticism characterised by?
reduced capacity to produce cortisol AND aldosterone
What is atypical hypoadrenocorticism characterised by?
Glucocorticoid deficiency only
What are the two main reasons for adrenocorticolysis
Immune mediated destruction
Increased ACTH –> haemorrhage and necrosis of adrenal
What is the typical signalment?
Young to middle aged dogs, more uncommon but does happen in middle aged cats
More common in females in dogs
What breeds are predisposed?
Standard poodle
Bearded Collie
Leonburgers
NSDT (Nova Scotia Duck Tolling) retrievers (the ones with the webbed feet)
What are the two clinical pictures with hypoA
Acutely collapsed severely compromised patient
Variably subtle ‘unwell’ animal, presents because not quite himself, waxes and wanes
How does the severely compromised hyoA patient present?
hypovolaemic and/or dehydrated
Poor circulatory volume-shock
Tachycardic or bradycardic or neither..
may be sudden on set or after relapsing more subtle set of problems
Why might they be tachycardic?
hypovolaemia
Why might they be bradycardic?
hyperkalaemia
Why does melena happen with hypoA
hypoA causes structural GIT problems
What will a gut biopsy from a hypoA dog be interpreted as?
IBD
Clin signs are non specific: decreased appetite, decreased exercise tolerance, depressed etc
non specific but a key differential as a very important and severe disease!
What are the common clinpath signs with hypoA?
possible mild anaemia, may be regenerative (melena bleeding), or non regenerative (anemia of chronic disease)
Hypoproteinaemia (pan) due to bleeding into gut
Absence or opposite of stress leukogram - eosinophilia, lymphoctosis
Azotaemia as hypovolaemic
Hyponatraemia and/or hyperkalaemia
Hypercalcaemia
hypoglycaemia
Why do you get the structural gut disease?
Lysosomal instability as lack of glucocorticoids
Why do you have inappropriately dilute urine?
Hyponatraemia - countercurrent doesn’t work so can’t concentrate urine
What tends to happen to electrolytes in hypoA?
Low serum sodium, high serum potassium as lacking ALDOSTERONE so can’t exchange in DCT of nephron
Is sodium potassium ratio diagnostic?
No!
Why is it such a bummer if you miss this disease?
Young dogs, easily treatable disease
What is the best way of assessing this disease?
ACTH stimulation test
Basal cortisol test if this not possible.
make sure hasn’t had any exogenous GC given! will mess up result
What is tetracosactide?
Synthetic ACTH. Used for ACTH stim test
How should you treat the severely compromised hypoA patient?
Supportive fluid therapy (but be careful as particularly fluid sensitive)
IV Hormone supplementation, must have good glucocorticoid AND mineralocorticoid activity
What is the maximum fluid dose rate you can give a hypoA patient?
7-8ml/kg/hr
Do you want to give short or long acting hormone replacement in the addisonian patient?
Short acting, i.e. NOT dex
What is the hormone replacement of choice? (drug name)
Hydrocortisone sodium succinate
Why must you not give dexamethasone in the addisonian situation?
Half life of 40 hours, if you give it and it hasn’t got hypoA it’s going to now have a long acting GC that’s going to potentially cause gut damage. It’s a very potent GC and has no MC activity
When do you move them onto oral treatment?
Once they start eating and drinking (usually within 36 hours)
What is the treatment for a patient with the chronic clinical picture?
Suitable balanced glucocorticoid and mineralocorticoid supplementation
What drugs are available for oral supplementation?
Fludrocortisone (MC and GC activity) Often need to supplement with either Cortisone acetate or Prednisolone
What dietary conditions should you consider?
Added salt
What is the normal cortisol production in the dog?
0.2mg/kg/24h
How do you work out how much you should supplement the dog with?
Work out how much the body would produce (0.2mg/kg/day)
Pred is around 5x as potent as the body’s own GC so divide the amount by 5
Why might you get altered gait when treating for hypoA?
pseudomyetonia from iatrogenic overdose
What other drugs can we use to manage stable patients?
Can use hydrocortisone acetate
How do you supplement atypical hypoA?
GC supplementation only
How do you monitor response?
Clinical picture improving
Check for stress leukogram
Sodium and potassium levels
ACTH stim/basal ACTH unnecessary and expensive
