CHAPTER 26 HYPERADRENOCORTICISM, CANINE 395
Iatrogenic HAC:
Clinically indistinguishable from the naturally occurring disease
Results from excessive or prolonged exogenous administration (systemic and/or
topical, including otic) of glucocorticoids
Causes bilateral adrenal atrophy and suppressed ACTH levels.HAC is a multisystemic disorder; the degree to which each system is involved varies
considerably; in some patients, signs referable to one system may predominate; others
have multiple systems affected.Urinary tract and/or dermatologic abnormalities are most often the first to be noticed.
SIGNALMENT/HISTORY
Considered one of the most common endocrine disorders in dogs.
Dogs: poodles, dachshunds, Boston terriers, boxers, and beagles are reportedly at
increased risk.
Predominantly female.
HAC is usually a disorder of middle-aged to older animals.
CLINICAL FEATURES (Figures 26.1–26.9)
Polyuria and polydipsia: occur in 85–95% of cases; glucocorticoids interfere with
antidiuretic hormone (ADH) release, resulting in compensatory polyuria and poly-
dipsia.Polyphagia: direct stimulatory effect on the appetite.
Abdominal distension (“pot belly”) occurs due to redistribution of fat, wasting of the
abdominal muscles, and hepatomegaly.
Hepatomegaly: accumulation of glycogen.
Hair loss: bilateral and symmetric truncal alopecia with sparing of the head and
extremities; atrophy of the hair follicles, epidermis, and adnexal structures; may see
alopecia along the bridge of the nose.Atrophy of the skin: decreased epidermal turnover/regeneration; decreased elasticity.
Phlebectasia: small, red, slightly raised areas that represent abnormal vessel dilation,
extension, or duplication.
Demodicosis: proliferation ofDemodexmites due to immunosuppression; rare.
Poor wound healing: excessive glucocorticoids suppress the inflammatory response,
fibroblast proliferation, and collagen deposition.
Comedones: plugged follicular ostia with keratin, black or white; sometimes associ-
ated with demodicosis.
Calcinosis cutis: accumulation and deposition of calcium in the dermis and/or sub-
cutis and along the follicular epithelium, which is palpable as firm gritty nodules
or plaques, yellow-pink in color; subsequent foreign body reaction; large coalescing
plaques are typically prominent in the dorsal neck region, milder cases are often most
pronounced in the ventral intertriginous areas (axillae, groin).