Hyperadrenocorticism affects many adult dogs. Whether the disease is pituitary-dependent (80% to 85% of spontaneous cases)
or adrenal-dependent (15% to 20% of cases), the clinical and laboratory abnormalities associated with it result from chronic
hypercortisolemia. Clinical signs of hyperadrenocorticism at the time of diagnosis can vary widely, and they develop so gradually
that owners often mistake the signs for "normal" aging. Being aware of the more subtle signs of canine hyperadrenocorticism
can be key to early diagnosis and initiation of therapy.
COMMON CLINICAL SIGNS OF CANINE HYPERADRENOCORTICISM
Whenever possible, pituitary-dependent hyperadrenocorticism and adrenal tumors should be differentiated to help guide therapy
and patient monitoring. Early diagnosis and management of canine hyperadrenocorticism may not only improve the patient's clinical
signs but may also keep the more severe consequences of Cushing's syndrome from developing.
CASE FILE: MITCH 12-year-old neutered male dachshund weighing 22 lb (10 kg)
Patient history and initial diagnostic workup
Mitch was presented to his primary care veterinarian for evaluation of polyuria and polydipsia of six months' duration. The
dog's urine specific gravity was 1.010 and a serum chemistry profile revealed an alkaline phosphatase activity of 1,240 IU/L
(reference range 37 to 105 IU/L). The results of a complete blood count were within normal limits, and urine bacterial culture
results were negative.
Adrenal function test results
The results of an adrenocorticotropic hormone (ACTH) stimulation test revealed a baseline cortisol concentration of 3.6 μg/dl
(reference range = 1.4 to 5 μg/dl) and a one-hour post-ACTH cortisol concentration of 12.9 μg/dl (reference range = 5.5 to
20 μg/dl). Low-dose dexamethasone suppression (LDDS) test results revealed a resting cortisol concentration of 9.1 μg/dl (reference
range 1.4 to 5 μg/dl) with four- and eight-hour post-dexamethasone cortisol concentrations of 5.6 μg/dl and 2.3 μg/dl (reference
range < 1.4 μg/dl), respectively.
The abnormal LDDS eight-hour cortisol concentration, in combination with more than 50% suppression in cortisol concentration
during the test, was diagnostic of pituitary-dependent hyperadrenocorticism (PDH). Mitch was referred to VCA West Los Angeles
Animal Hospital to be evaluated for treatment.