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Hyperadrenocorticism 485

Hyperadrenocorticism Bonus Material Client Education
Sheet
Online
VetBooks.ir Diseases and Disorders
BASIC INFORMATION
○ Alopecia and weakness are common.
○ Less common are lethargy, poor hair • Iatrogenic HAC can be due to exogenous
glucocorticoid administration by any route.
Definition regrowth, issues related to infertility,
• Spontaneous hyperadrenocorticism (HAC) is bruising, and calcinosis cutis. DIAGNOSIS
a disorder caused by excessive adrenocortical ○ With a pituitary macroadenoma, anorexia,
cortisol production. ataxia, disorientation, and uncommonly, Diagnostic Overview
• Iatrogenic HAC results from exogenous seizures The suspicion that a patient has HAC is based
glucocorticoid administration. • Cats on the history and physical exam. Endocrine
○ Approximately 80% of cats with HAC tests should be performed only when clinical
Synonyms have DM with associated complaints signs consistent with HAC are present. No test
• Hypercortisolemia (p. 251). for the diagnosis of HAC is 100% accurate,
• Cushing’s syndrome: constellation of clinical ○ PU/PD uncommon in cats if DM not and misdiagnosis and overdiagnosis may occur.
signs due to excess glucocorticoid also present
• Cushing’s disease: pituitary-dependent HAC ○ Bilaterally symmetrical alopecia uncom- Differential Diagnosis
mon in cats with HAC, but thin skin Depends on clinical and laboratory
Epidemiology can be severe, leading to spontaneous abnormalities:
SPECIES, AGE, SEX wounds • Hypothyroidism (p. 525)
• Common in dogs, rare in cats • Alopecia X (p. 44)
• Dogs PHYSICAL EXAM FINDINGS • Sex hormone-secreting tumors (p. 35)
○ Middle-aged to older; rare in dogs < 6 years • Dogs • DM (p. 251)
○ Possible predisposition toward females overall ○ Common findings include pendulous • Causes of PU/PD (p. 812)
• Cats: middle-aged to older; no known sex abdomen, bilaterally symmetric alope- • Causes of polyphagia (p. 809)
predisposition cia, panting, hepatomegaly, and muscle • Causes of alopecia (p. 47)
weakness. • Causes of panting (p. 1263)
GENETICS, BREED PREDISPOSITION ○ Less common findings include thin skin,
• Dogs comedones, hyperpigmentation, and Initial Database
○ Can occur in any breed pyoderma. • CBC: leukocytosis with mature neutrophilia,
○ Poodles, dachshunds, and boxers predis- ○ Uncommon findings are calcinosis eosinopenia, and lymphopenia in most dogs;
posed; German shepherds, Boston terriers, cutis, bruising, testicular atrophy, facial monocytosis, thrombocytosis, and mild
and beagles may be predisposed. nerve palsy, respiratory distress (due to erythrocytosis are less common. In cats,
○ Dogs with adrenal tumors (ATs) more pulmonary thromboembolism), ligament lymphopenia is most common finding.
likely to be > 20 kg. rupture, pseudomyotonia, neurologic signs • Serum chemistry
• Cats: no known breed predisposition such as ataxia and disorientation due to ○ High cholesterol and liver enzymes
space-occupying effects of a pituitary (with elevation in alkaline phosphatase
RISK FACTORS macroadenoma, and space-occupying [ALP] greater than that of alanine ami-
Administration of any form of exogenous steroid effects of an AT such as rear limb edema. notransferase [ALT]); ALP activity high
by any route can cause iatrogenic HAC; the • Cats: pendulous abdomen, unkempt haircoat, in approximately 90% of dogs with HAC.
more potent the steroid and the more chronic alopecia, thin skin, and muscle wasting Only about 33% of affected cats have
the use, the more likely is iatrogenic HAC. elevated ALP values.
Etiology and Pathophysiology ○ Hyperglycemia common; about 10% of
ASSOCIATED DISORDERS • Dogs dogs and 80% of cats with HAC have
• Urinary tract infections ○ Approximately 85% of cases of spontane- concurrent DM.
• Pyoderma ous HAC (i.e., noniatrogenic) are due to • Urinalysis: low specific gravity (usually
• Calcium oxalate urolithiasis PDH. A pituitary corticotroph tumor < 1.020) and proteinuria common; pyuria
• Systemic hypertension oversecretes ACTH, leading to bilateral may or may not be present with bacteriuria.
• Diabetes mellitus (DM): more likely to occur adrenocortical hyperplasia and oversecre- • Abdominal radiographs: hepatomegaly
in cats with HAC than in dogs tion of cortisol. Tumor almost always common; occasionally, cystic calculi, adrenal
• Protein-losing nephropathy benign with nontumorous hyperplasia, mass with or without mineralization
• Neurologic signs with pituitary macroadenoma and adenocarcinomas are rare. • Thoracic radiographs: bronchial mineraliza-
• Pulmonary thromboembolism ○ Anterior pituitary involved in approxi- tion possible; may see changes consistent
• Ligament and tendon injury mately 80%-85% of PDH cases, interme- with pulmonary thromboembolism (p. 842)
diate lobe of pituitary in the remaining • Blood pressure: in dogs, hypertension
Clinical Presentation cases common but usually mild
DISEASE FORMS/SUBTYPES ○ Pituitary macroadenomas (>1 cm in
• Pituitary-dependent HAC (PDH) diameter) occur in 10%–25% of PDH Advanced or Confirmatory Testing
• Adrenal tumor HAC (ATH) cases. Endocrine testing required to make a diagnosis
• Iatrogenic HAC ○ In the remaining 15%-20% of spontaneous of HAC.
HAC cases, ATH is present; approximately • Cannot administer prednisone, prednisolone,
HISTORY, CHIEF COMPLAINT one-half of ATs are malignant. hydrocortisone, or methylprednisolone
• Dogs ○ Food-induced HAC (p. 489) and ectopic within 12 hours before a test that measures
○ Classic complaints are polyuria/polydipsia ACTH secretion are rare causes of HAC. cortisol (test interference)
(PU/PD), polyphagia, a potbellied appear- • Cats: types appear similar to dogs; AT more To screen for HAC: ACTH stimulation test,
ance, and panting. likely to be malignant. low-dose dexamethasone suppression test

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