Hypoadrenocorticism Flashcards
Where is glucocorticoids secreted in the adrenal gland?
Adrenal cortex, in all 3 layers (zone glomerulus, fasciculata, and reticularis)
Where is aldosterone (mineralocorticoid) secreted in the adrenal gland?
In the zone glomerulus only - only place that has aldosterone synthase
What is a possible cause of hypoadrenocorticism in dogs?
immune-mediated
Which breeds have familial predisposition to hypoadrenocorticism?
- Leonberger
- Great Dane
- Standard Poodle, Portugese Water Dog, Pomeranaina - autosomal recessive
- Bearded Collie - complex
- Cocker Spaniels
What’s the definition of primary hypoadrenocorticism in dogs? What’s atypical Addison’s?
hypoadrenocorticism = atrophy of adrenal cortices
- so deficient in both mineralocorticoids and glucocorticoids
- Atypical Addison’s = Na+/K+ values remain normal (Addison’s = hyponatremia, and hyperkalemia)
- sometimes atypical Addison’s can progress to full-on Addison’s
- rare have mineralocorticoid deficiency proceed glucocorticoid deficiency
- even more rare to have just aldosterone deficiency
What are some less common causes of hypoadrenocorticism in dogs?
Secondary to direct invasion of the adrenal gland
- neoplasia = most common
- infectious: TB, fungal, other granulomatous diseases, infarct
What causes secondary hypoadrenocorticism in dogs?
- dysfunction of the hypothalamus or pituitary gland
- could be due to neoplasia, infection, inflammation, trauma, infarct
- will have low CRH or ACTH
- won’t effect mineralocorticoids
- difference between that and atypical Addison’s is that secondary hypoadrenocorticism will have low ACTH versus atypical Addison’s will have high ACTH
Which breeds are at a DECREASED risk f hypoadrenocorticism?
- Golden retrievers
- Yorkies
- Pitties
- Chihuahuas
- Lhasa Apsos
What’s the typical signalment for hypoadrenocorticism in dogs?
- young to mid aged (3-4y = median)
- female may be at an increased risk
- breed disposition
**What are some clinical signs of hypoadrenocorticism in dogs?
Mostly attributable to lack of cortisol
- decreased appetite
- weigh loss*
- vomiting*
- diarrhea*
- PU/PD**
- lethargy*
- weakness*
- shaking***
- collapse (extreme)
due to lack of protection of GI mucosa from acidity
**due to lack of mineralocorticoids (aldosterone), leading to Na+ loss
**due to hypoglycemia
What’s the action of glucocorticoids on glucose homeostasis?
In stressful or fasting conditions
- catabolism of glycogen
- stimulates gluconeogenesis
What are some PE abnormalities for hypoadrenocorticism in dogs?
- dehydration (PU/PD, from Na+ excretion)
- hypotension, mainly systolic (glucocorticoids enhances vascular effects of angiotensin and renin)
- bradycardia (hyperkalemia, takes longer to repolarize)
- abdominal pain (glucocorticoids have protective effects on GI mucosa)
What are some common CBC finding for hypoadrenocorticism in dogs?
- increased lymphocyte counts (>2000 = 58% sensitive and 85% specific for hypoadrenocorticism)
- lower neutrophils
- higher eosinophils
What electrolyte abnormalities can be seen with hypoadrenocorticism in dogs? Why?
- hyponatremia (lack of aldosterone leading to Na+ excretion)
- hyperkalemia (Lack of aldosterone leading to K+ retention)
- hypochloremia (follow Na+ from blood to urine)
- hypercalcemia (glucocorticoids facilitates calciuresis, maybe acidic environment [lack of aldosterone = lack of H+ secretion] displaces Ca+ from albumin due to competition). But it’s usually total Ca elevated, not iCa
What’s the MOA of abnormal glucose level in dogs with hypoadrenocorticism?
lack of glucocorticoids = decreased gluconeogenesis and glycogen catabolism
- the hypoglycemia tend to mild, and seizure in uncommon
What’s the reason of increased liver enzymes, low albumin, and low cholesterol for dogs with hypoadrenocorticism?
- it’s not due to liver dysfunction
- likely due to acute GI ischemia
What’s the likelihood of resolving severe serum biochemistry abnormalities in dog with hypoadrenocorticism?
they almost always completely resolve with treatment!
What are some ECG changes noted with hyperkalemia?
lack of P wave, wide QRS, tall T waves
- heart block
Can AUS be used to assess adrenal function?
No, but dog with hypoadrenocorticism, adrenals are typically <3mm
**What is the best test to confirm hypoadrenocorticism in dogs?
ACTH stim
baseline and post ACTH cortisol level would be <1mcg/dL
Can resting cortisol alone be enough to diagnose hypoadrenocorticism in dogs?
no, but you can do cortisol: endogenous ACTH ratio
it’s a good rule out screening test
What are some ddx for hypoadrenocorticism?
severe GI diseases can lead to electrolyte abnormalities –> tricuriasis, salmonellosis
- periparturient iillness
- chylothorax
**How to treat an acute hypo adrenal crisis in dogs?
1 = fluids! 0.9% NaCl, though acidic, it has more NaCl than K. The acidosis usually will correct itself
- if the electrolyte imbalance remains, need to correct Na+ slowly to ovoid osmotic shift
- can use IV dextrose to stimluate endogenous insulin secretion to drive the K+ intracellular
- IV insulin only used if glucose level is above 11mmol/L, watch for hypoglycemia
- hyperglycemia can also decrease Na+ level due to fluid shifting (dilution)
- if severe acidosis is not resolved, can consider doing bicarbonate
- can also give DOCP once ACTH stim done and other ddx excluded
- usually steroids are not needed in the acute setting and can complete ACTH stim first
- if really need steroids, use dexamethasone instead (won’t cross react with cortisol assay and acts quickly), but can suppress endogenous ACTH/CRH, and effect ACTH stim results
What’s the long term treatment for hypoadrenocorticism in dogs?
maintenance therapy can usually begin 24-48h post crisis.
Goals = supplement glucocorticoids and mineralocorticoids
- Glucocorticoids: prednisone. initially start high, and taper to lowest effective dose
- Mineralocorticoids: DOCP. SQ injection done every 3 weeks. Monitor Na:K ratio half way and on the day it’s due. If >32, then skip. If < 28, give. Adjust dosage and interval as needed
- fludrocortisone: has both glucocorticoid and mineralocorticoid activity, but it’s harder to tailor to minimize the side effects of steroids
- DOCP is more effective vs fludrocortisone in decreasing the plasma renin activity, increasing Na and decreasing K
How is hypoadrenocorticism monitored?
- frequent blood work monitoring the Na:K ratio
- PU/PD could be a sign of steroid side effect, HA, or other common conditions
- need to monitor atypical Addison’s closely too as they progress to typical Addison’s
What’s the long term prognosis for hypoadrenocorticism in dogs?
Excellent, once recovered from acute crisis
Give a brief description of hypoadrenocorticism in cats.
Rare in cats. but similar presentation and test abnormalities as dogs. Same treatment but prognosis is not as good as dogs.
Can have pseudo hyponatremia and hyperkalemia from peritoneal effusion
