Canine Pituitary and Adrenal Diseases & Pheochromocytoma

Question 1

What is the most common cause of Addison’s disease?

Answer 1

primary adrenal faliure due to immune destruction of the adrenal gland

• secondary pituitary failure is rare

Question 2

What are 2 causes of iatrogenic Addison’s disease?

Answer 2

1. prolonged use or high doses of Mitotate or Trilostane
2. prolonged use of glucocorticoids causes adrenal atrophy and an abrupt stop without tapering does not allow time for the adrenal gland to adjust

Question 3

What is the difference between typical and atypical hypoadrenocorticism?

Answer 3

TYPICAL = glucocorticoid AND aldosterone deficient results in hyponatremia and hyperkalemia, usually due to an abnormal adrenal cortex

ATYPICAL = glucocorticoid deficient with normal aldosterone results is normal Na/K, usually due to primary adrenal disease or a decreased in ACTH from the pituitary (aldosterone secreted in response to activation of RAAS, not ACTH)

Question 4

What is the most common signalment in patients with Addison’s disease? What breeds are predisposed?

Answer 4

mean 4.5 y/o female dogs

• Bearded Collie
• Standard Poodle
• Nova Scotia DTR
• Portuguese Water Dog
• Great DAne
• Westies
• Basset Hounds

Question 5

What are the most common signs associated with acute onset Addison’s disease?

Answer 5

• bradycardia
• melena
• hematochezia

due to shock to GI

Question 6

What are the most signs associated with gradual onset Addison’s disease?

Answer 6

• GI: anorexia, vomiting, diarrhea
• lethargic, weak
• PU/PD —> hyponatremia
• collapse

(look like dogs with GI disease)

Question 7

What are the 4 most common things seen on CBC in patients with Addison’s disease?

Answer 7

1. lack of stress leukogram (no cortisol!) - neutrophilia without lymphopenia
2. lymphocytosis
3. eosinophilia
4. mild non-regenerative anemia - GIT bleeding may cause it to become regenerative

Question 8

What are the 10 most common findings on biochemistry in patients with Addison’s disease? What acid-base abnormality is seen?

Answer 8

1. pre-renal azotemia
2. hypercalcemia
3. hyperkalemia
4. hyperphosphatemia
5. hypoalbuminemia
6. hypochloremia
7. hypocholesterolemia
8. hypoglycemia - cortisol stimulates gluconeogenesis and glycogenolysis
9. hyponatremia
10. increased liver enzymes

metabolic acidosis

Question 9

What is seen on UA in patients with Addison’s? Why is this significant?

Answer 9

< 1.030, minimally concentrated

not concentrated despite pre-renal azotemia (dehydration), due to increased water loss caused by hyponatremia

Question 10

What imaging can be performed to diagnose Addison’s disease?

Answer 10

• ultrasound: thin adrenals
• thoracic radiographs: microardia, decreased caudal vena cava size due to hypoperfusion

Question 11

What are 3 other manifestations of Addison’s disease?

Answer 11

1. severe GI hemorrhage (cortisol required for health and growth of GI mucosa)
2. megaesophagus
3. hypoglycemia

Question 12

What test is used to diagnose Addison’s? What is used for confirmation?

Answer 12

baseline cortisol - >2mg/dL = NOT Addison’s; <2mg/dL = COULD be Addison’s

ACTH stim - pre and post <1

Question 13

What is recommended for Addison’s disease treatment?

Answer 13

• glucocorticoid replacement
• mineralocorticoid replacement

Question 14

What 2 options are available for glucocorticoid replacement for Addison’s disease treatment?

Answer 14

1. injectable Dexamethasone - doesn’t cross-react with assay, can be given to crashing patients before diagnosis, may be needed for patients that cannot take pills
2. Prednisone - can cause false negatives of ACTH stim

Question 15

What 2 options are available for mineralocorticoid replacement for Addison’s disease treatment?

Answer 15

1. Fludrocortisone (Florinef) - daily, oral
2. Desoxycortisoterone pivalate (DOCP) - monthly injectable

Question 16

What is the most life-threatening electrolyte abnormality associated with Addison’s disease? What are 3 treatments?

Answer 16

hyperkalemia

1. fluids - dilution
2. glucose and regular insulin - shunts K into cells
3. calcium gluconate - protects heart from conduction issues while K is being decreased

Question 17

What is pheochromocytoma? What does this result in?

Answer 17

tumor of the adrenal medulla, resulting in dysregulated catecholamine release (norepinephrine, epinephrine)

• vasoconstriction, hypertension
• tachyarrhythmia
• vasodilation of smooth muscles, collapse

Question 18

What is the most common signalment associated with pheochromocytoma? What are the most common signs?

Answer 18

11 y/o with no breed or sex predilection

episodic and variable:

• weakness, lethargy, anorexia, collapse
• tachyarrhythmias, tachypnea
• retinal hemorrhage, pale MM
• PU/PD
• muscle tremors, seizures, anxiety, pacing

Question 19

What are the 2 most common signs seen with pheochromocytomas?

Answer 19

1. tachyarrhythmias - typically ventricular
2. hypertension due to increased HR, contractility, and vasoconstriction - retinal hemorrhage

Question 20

What imaging is used to diagnose pheochromocytoma?

Answer 20

AUS and CT - evaluates adrenal gland size and vascular invasion (embolism) of the tumor, as well as metastatic lesions

Question 21

What is the best test to diagnose pheochromocytoma? What is diagnostic?

Answer 21

urinary normetanephrine:creatinine ratio

> 4x upper limit —> can overlap in dogs with hyperadrenocorticism or non-adrenal illness, but these instances will not be as high of a result

Question 22

What is the treatment of choice of pheochromocytoma? What can be done before?

Answer 22

surgical removal of tumor

• treat hypertension with Amlodipine
• Phenoxybenzamine alpha-blocker to stabilize