Hypoadrenocorticism Flashcards
Where are mineralocorticoids (aldosterone) secreted from?
Zona glomerulosa
Where are glucocorticoids (cortisol) secreted from?
Zona fasciculata
What is primary hypoadrenocorticism due to?
Destruction/ infiltration of adrenal cortices
How much of both glands must be destroyed before signs are apparent?
90%
What is the most common cause of primary HOC?
Immune mediated destruction
What is secondary HOC due to and what does it cause?
Lack of ACTH production
Very uncommon
Aldosterone production is unaffected
Signs reflect lack of cortisol
What can cause iatrogenic HOC?
Abrupt withdrawal of exogenous steroids
Therapy for HC with trilostane or mitotane
What are signs of cortisol deficiency?
Anorexia, vomiting, diarrhea, lethargy, depression, weight loss, abdominal pain
What does aldosterone do?
Increase blood volume, grabs salt and water
What are signs of aldosterone deficiency?
Weakness, hypotension, dehydration, pre-renal azotemia, cardiac consequences of hyperkalemia (bradycardia, irregular beats, sinus arrest)
What is the common signalment for HOC?
young, female, breed predisposition (portuguese water dog, standard poodle, west highland terrier)
ANY DOG
Rare in cats
What are the chief complaints for HOC?
ADR
Commonly suggests GI disease
The great pretender
Signs may be triggered by a stressful event
Most patients appear to have GI or renal disease
What causes most dramatic signs?
Lack of aldosterone
What are common CBC findings in patients with HOC?
anemia is common, lack of stress leukogram, eosinophilia is a classic marker for HOC
Always consider HOC in a sick dog with eosinophils greater than
500
What chem findings are common in patients with HOC?
Low sodium
High potassium
High phosphate
Low chloride
High calcium
What sodium:potassium ratio is suggestive of HOC?
<1:27
What chemistry changes will you see in a dog with lack of cortisol?
Hypoglycemia
Hypocholesterolemia
Hypoalbuminemia
What chemistry changes will you see in a dog with lack of aldosterone?
Azotemia
Electrolyte changes
What would you expect to see in a UA in a HOC patient?
Low urine specific gravity
What additional changes might be seen on radiographs?
Microcardia
Pulmonary hypoperfusion
Megaesophagus
What ultrasonic change might be seen on ultrasound?
Small adrenal glands (<3.7 mm)
When should you consider HOC as a differential?
Patient has waxing and waning non-specific illness with anorexia and lethargy
Episodes of disease seem to be triggered by stressful events
Any patient with GI disease
Any patient with azotemia
Any patient with hyponatremia or hyperkalemia
Any patient with hypoglycemia
What baseline cortisol is highly suggestive of HOC?
<2 mcg/dl
When running an ACTH stim test, what post acth stim cortisol confirms HOC?
< 3 mcg/dl
Dogs with primary HOC will have very low ____ and very high ____.
Very low cortisol
Very high ACTH
What fluids does the NAVLE want for patients in an Addisonian crisis?
0.9% NaCl unless sodium is <130 mmol/L
What are ways to manage hyperkalemia?
Bolus dextrose, beta agonists (Terbutaline, Albuterol), calcium gluconate (need ECG monitoring), insulin (LAST OPTION)
What is a fast aldosterone replacement used to bridge before giving DOCP?
Fludocortisone
What should be used for glucocorticoid replacement?
Prednisone (0.5-1 mg/kg/day)/prednisolone (0.3 mg/kg/day)
Taper down to lowest effective dose over 4 weeks
What should be used for mineralocorticoid replacement?
DOCP SQ every 25 days
Not necessary unless serum electrolytes are abnormal
When should patients be rechecked when given DOCP?
Day 12 and 25
