6-year-old female spayed Swiss Mountain dog was referred to the Cornell University Hospital for Animals Internal Medicine Service from the Community Practice Service (CPS) for a one-year history of waxing and waning gastrointestinal signs and a several month course of lethargy. Routine hemogram and serum biochemistry profile performed by CPS on the patient revealed findings suggestive of Addison's disease. A baseline cortisol concentration was subsequently submitted and discovered to be subnormal.

On presentation to the Internal Medicine Service, the dog was bright, alert, and responsive with no significant abnormalities detected on physical examination. Serum electrolyte panel confirmed the previously detected hyperkalemia. Cortisol concentration following administration of exogenous ACTH was subnormal. Endogenous ACTH concentration was increased.

These collective findings were indicative of primary hypoadrenocorticism (Addison's disease). Mineralocorticoid (desoxycorticosterone pivalate [DOCP]) and glucocorticoid (prednisone) replacement therapy was initiated. The dog has been well-controlled on these medications for the past three months.