Hyperadrenocorticism (Cushing's Disease)

Question 1

What are 6 key clinical signs associated with Cushing’s? What else may be seen?

Answer 1

1. PU/PD
2. panting
3. polyphagia
4. pendulous belly
5. pyoderma
6. thin skin

pigmentation and symmetrical alopecia

Question 2

What are the 3 possible causes of Cushing’s in dogs?

Answer 2

1. ACTH secreting pituitary tumors
2. cortisol secreting adrenal tumors
3. iatrogenic steroid administration

Question 3

What unique clinical sign is seen in horses with Cushing’s?

Answer 3

hirsutism - abnormal, long, wavy coat

Question 4

What are 3 signs of Cushing’s on routine bloodwork?

Answer 4

1. stress leukogram - neutrophilia, lymphopenia
2. elevated ALP
3. hyposthenuria - <1.010

Question 5

What are the 2 most common diagnostic tests used for diagnosing Cushing’s?

Answer 5

1. LDDST - measure plasma cortisol before and at 4 and 8 hours after IV dexamethasone (0.01 mg/kg)
2. ACTH stimulation test - measure cortisol levels before and after administrating ACTH

Question 6

How is a LDDST interpreted in a potentially Cushingoid patients?

Answer 6

90% of dogs with Cushing’s will have 8 hour cortisol levels >1.4 ug/dL

• to differentiate pituitary-dependent hyperadrenocorticism vs and adrenal tumor, look at the 4 hour value –> <50% basal value = PDH

Question 7

When is an ACTH stimulation test most commonly performed in a potentially Cushingoid patient?

Answer 7

more commonly done to monitor therapy for hyperadrenocorticism

Question 8

What imaging is most commonly done in potentially Cushingoid patients?

Answer 8

abdominal U/S to view an adrenal mass vs. bilaterally enlarged adrenal glands with PDH

Question 9

What urinary test can be done to diagnose potential Cushing’s disease? How does this compare to other diagnostics?

Answer 9

urine cortisol:creatinine ratio

high sensitivity, low specificity = many false positives = negative rules out Cushing’s

Question 10

Other than a LDDST, what 2 other tests can be used to differentiate a pituitary-dependent hyperadrenocortism and an adrenal tumor?

Answer 10

1. endogenous ACTH - high plasma ACTH with PDH, low ACTH with AT (expensive!)
2. HDDST

Question 11

What is atypical Cushing’s? What test can be used to diagnose it?

Answer 11

patient presents with clinical signs associated with Cushing’s, but diagnostics are WNL - hypothesized to be caused by a relative deficiency in some of the enzymes critical to the synthesis of cortisol

170-hydroxyprogesterone testing

Question 12

What are the 2 most common treatments of Cushing’s in dogs? How do they work?

Answer 12

1. Mitotane (o,p’DDD) - causes adrenocorticolysis (chemical adrenalectomy) –> must monitor ACTH stimulation tests to avoid causes Addison’s
2. Trilostane - oral steroid analogue that inhibits cortisol and aldosterone synthesis

Question 13

What are 3 possible treatments for horses with Cushing’s?

Answer 13

1. Pergolide
2. Trilostane
3. Cyproheptadine