Hypoadrenocorticism

Question 1

Where is glucocorticoids secreted in the adrenal gland?

Answer 1

Adrenal cortex, in all 3 layers (zone glomerulus, fasciculata, and reticularis)

Question 2

Where is aldosterone (mineralocorticoid) secreted in the adrenal gland?

Answer 2

In the zone glomerulus only - only place that has aldosterone synthase

Question 3

What is a possible cause of hypoadrenocorticism in dogs?

Answer 3

immune-mediated

Question 4

Which breeds have familial predisposition to hypoadrenocorticism?

Answer 4

• Leonberger
• Great Dane
• Standard Poodle, Portugese Water Dog, Pomeranaina - autosomal recessive
• Bearded Collie - complex
• Cocker Spaniels

Question 5

What’s the definition of primary hypoadrenocorticism in dogs? What’s atypical Addison’s?

Answer 5

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

Question 6

What are some less common causes of hypoadrenocorticism in dogs?

Answer 6

Secondary to direct invasion of the adrenal gland
- neoplasia = most common
- infectious: TB, fungal, other granulomatous diseases, infarct

Question 7

What causes secondary hypoadrenocorticism in dogs?

Answer 7

• 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

Question 8

Which breeds are at a DECREASED risk f hypoadrenocorticism?

Answer 8

• Golden retrievers
• Yorkies
• Pitties
• Chihuahuas
• Lhasa Apsos

Question 9

What’s the typical signalment for hypoadrenocorticism in dogs?

Answer 9

• young to mid aged (3-4y = median)
• female may be at an increased risk
• breed disposition

Question 10

**What are some clinical signs of hypoadrenocorticism in dogs?

Answer 10

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

Question 11

What’s the action of glucocorticoids on glucose homeostasis?

Answer 11

In stressful or fasting conditions
- catabolism of glycogen
- stimulates gluconeogenesis

Question 12

What are some PE abnormalities for hypoadrenocorticism in dogs?

Answer 12

• 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)

Question 13

What are some common CBC finding for hypoadrenocorticism in dogs?

Answer 13

• increased lymphocyte counts (>2000 = 58% sensitive and 85% specific for hypoadrenocorticism)
• lower neutrophils
• higher eosinophils

Question 14

What electrolyte abnormalities can be seen with hypoadrenocorticism in dogs? Why?

Answer 14

• 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

Question 15

What’s the MOA of abnormal glucose level in dogs with hypoadrenocorticism?

Answer 15

lack of glucocorticoids = decreased gluconeogenesis and glycogen catabolism
- the hypoglycemia tend to mild, and seizure in uncommon

Question 16

What’s the reason of increased liver enzymes, low albumin, and low cholesterol for dogs with hypoadrenocorticism?

Answer 16

• it’s not due to liver dysfunction
• likely due to acute GI ischemia

Question 17

What’s the likelihood of resolving severe serum biochemistry abnormalities in dog with hypoadrenocorticism?

Answer 17

they almost always completely resolve with treatment!

Question 18

What are some ECG changes noted with hyperkalemia?

Answer 18

lack of P wave, wide QRS, tall T waves
- heart block

Question 19

Can AUS be used to assess adrenal function?

Answer 19

No, but dog with hypoadrenocorticism, adrenals are typically <3mm

Question 20

**What is the best test to confirm hypoadrenocorticism in dogs?

Answer 20

ACTH stim
baseline and post ACTH cortisol level would be <1mcg/dL

Question 21

Can resting cortisol alone be enough to diagnose hypoadrenocorticism in dogs?

Answer 21

no, but you can do cortisol: endogenous ACTH ratio
it’s a good rule out screening test

Question 22

What are some ddx for hypoadrenocorticism?

Answer 22

severe GI diseases can lead to electrolyte abnormalities –> tricuriasis, salmonellosis
- periparturient iillness
- chylothorax

Question 23

**How to treat an acute hypo adrenal crisis in dogs?

Answer 23

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

Question 24

What’s the long term treatment for hypoadrenocorticism in dogs?

Answer 24

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

Question 25

How is hypoadrenocorticism monitored?

Answer 25

• 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

Question 26

What’s the long term prognosis for hypoadrenocorticism in dogs?

Answer 26

Excellent, once recovered from acute crisis

Question 27

Give a brief description of hypoadrenocorticism in cats.

Answer 27

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