Does this dog have Cushing’s disease?
Linda E. Luther, DVM, DACVIM (SAIM)
Small Animal Track
2012 ISVMA Annual Conference Proceedings
Hyperadrenocorticism (HAC)
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Two natural forms, one iatrogenic
Pituitary-dependent HAC (PDH) (80-85%)
o Functional tumor in pituitary gland
o Endogenous ACTH levels are inappropriately elevated
o Bilateral adrenal gland hyperplasia results
Adrenal tumor (AT) (15-20%)
o Referring to an adrenal cortical tumor vs. pheochromocytoma
o Not always functional
o 10% are bilateral
o Half are a benign adenoma, half a malignant adenocarcinoma
o Approximately half of all tumors mineralize
Iatrogenic
o Due to chronic exogenous glucocorticoid administration
o Parenteral or topical
Clinical signs of all three forms similar
Clinical signs/PE findings
 (All may not be present):
 PUPD
 Alopecia/hyperpigmentation
 Pot-bellied appearance
 Hepatomegaly
 Polyphagia
 Muscle weakness
 Panting
 Obesity
CBC, chemistry, bile acids
 Neutrophilia, monocytosis, lymphopenia
 Elevated ALP (85-95%)
 Mild increase in ALT
 Elevated cholesterol, triglycerides
 10% become diabetic
 Bile acids may be mildly elevated
Urinalysis
 Specific gravity is often less than 1.015-1.020
 May be able to concentrate up to 1.025-1.035
 Proteinuria is often present
 46% have UTI (sediment may be inactive)
Other clinical findings
 Hypertension
 Proteinuria
 Thromboembolism
CUSHING’S DISEASE IS A CLINICAL VS. LABORATORY DIAGNOSIS
 IF THE DOG DOES NOT HAVE CLINICAL SIGNS THAT ARE SUGGESTIVE OF HAC, ADRENAL
TESTING IS NOT RECOMMENDED.
 TEST RESULTS MAY BE MISLEADING IF SIGNIFICANT NONADRENAL DISEASE IS PRESENT.
Screening tests
 Low dose dexamethasone suppression test (LDDS)
o 85-95% sensitive; 70-75% specific
o May also diff b/w PDH and AT
o > 1.4 μg /dL at 8 hrs: Consistent with
hyperadrenocorticism
 ACTH stimulation test
o <60-85% sensitive;85-90% specific
 Urine cortisol:creatinine ratio
o 97% sensitive; 20% specific
CRH
ACTH
LDDS vs. ACTH stim
 More sensitive
 Lower cost
 Might ddx PDH v.s AT
ACTH stim indications
 Iatrogenic HAC
 Monitoring HAC tx
 Dx hypoadrenocorticism
CORTISOL
Once a diagnosis of HAC confirmed, these tests differentiate between PDH and AT
 LDDS
o 60% of PDH dogs have suggestive results (suppression at 4 h, but not at 8 h)
o Suppression =
 < 1.4 μg/dL at 4 hrs
 < 50% baseline at 4 hrs
 < 50% baseline at 8 hrs
 HDDS
o No suppression at 8 hours: 100% AT, 25% PDH
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Endogenous ACTH level
o < 20 pg/mL suggests AT
o > 45 pg/mL suggests PDH
o 20-45 pg/mL is nondiagnostic
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Abdominal ultrasound
o Rules out adrenal diseases, rules out nonadrenal disease
o Dogs with PDH may (or may not) have enlarged adrenal glands
CT/MRI
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Cases: Do these dogs have Cushing’s disease?
1. 8-year-old Fs Dachshund. History of PUPD. PE:
BCS 8/9, pot-bellied, ventral alopecia. ALP 4x
normal, Uspgr 1.035. LDDS pre: 6.8 μg/dL; 4 hr
post: 1.0 μg/dL; 8 hr post: 1.7 μg/dL.
2. 7-yr-old Fs Boxer. History of PUPD. PE: BCS 8/9, pot-bellied, ventral alopecia. ALP
6x normal, Uspgr 1.020. LDDS pre: 6.8 μg/dL; 4 hr post: 6.2 μg/dL; 8 hr post: 6.2
μg/dL. Ultrasound appearance of adrenal glands: Right adrenal gland irregular in
contour, oval-shaped, measures 3 x 6 cm. Left adrenal gland small.
3. 10-yr-old Mn Poodle. Presented for dental cleaning. No clinical complaints. PE: BCS
4/9, Grade 2 dental disease. Pre-anesthetic blood work showed ALP 10x normal.
LDDS pre 9.3 μg/dL; 4 hr post 3.0 μg/dL; 8 hr post 2.6 μg/dL.
4. 7-year-old Fs Pug. History of PUPD. PE: BCS 8/9, pot-bellied. ALP 6x normal, Uspgr
1.020. LDDS pre: 7.0 μg/dL; 4 hr post: 5.0 μg/dL; 8 hr. post: 4.0 μg/dL. Ultrasound
appearance of adrenal glands: Normal shape, cranial and caudal poles of both left and
right adrenal glands = 0.8 cm.
5. 10-year-old Mn Bassett hound. History PUPD, polyphagia. PE: BCS 9/9, pot-bellied,
thin hair coat. ALP 5x normal, ALT 2x normal, Uspgr 1.018. LDDS pre: 5.0 μg/dL; 4 hr
post: 4.9 μg/dL; 8 hr. post: 4.0 μg/dL. Ultrasound appearance of adrenal glands: Both
left and right adrenal glands round in shape, 2 cm in diameter. Endogeneous ACTH 32
pg/dL (> 45 pg/dL = PDH).
6. 7-yr-old Fs Lab. Three-month history of PUPD, polyphagia and weight loss. PE: BCS
7/9. ALP 6x normal, hyperglycemia (410 mg/dL), 3+ glucosuria, Uspgr 1.015. LDDS pre:
6.8 μg/dL; 4 hr post: 6.2 μg/dL; 8 hr. post: 6.2 μg/dL.
7. 8-year-old Mn Scottish Terrier. No clinical signs. PE: BCS 6/9. Senior wellness blood
work revealed ALP 8x normal. Bile acid assay WNL.
8. 10-year-old Mn Boston Terrier. History of vomiting and weight loss. PE: BCS 4/9.
ALP 10x normal, Uspgr 1.020. Urine cortisol/creatinine ratio 30 (normal 8-24).
9. 8-year-old Fs Cavalier King Charles spaniel. History of PUPD and anorexia. PE: BCS
5/9. ALP 7x normal, ALT 12x normal, Uspgr 1.026.
10. 9-year-old Mn Pomeranian. History of truncal alopecia. PE: BCS 7/9, sparse hair coat.
ALP 4x normal, Uspgr 1.020. LDDS pre: 3.0 μg/dL; 4 hr post: < 0.5 μg/dL; 8 hr. post:
< 0.5 μg/dL.
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