Hypocortisolism in a dog caused by bilateral pheochromocytoma

Abstract

We present a 12-year-old French bulldog with muscle weakness, epigastric pain, weight loss, high systolic blood pressure and cardiac arrhythmias. Physical and laboratory examination revealed no abnormalities. On a computed tomography scan, severely enlarged adrenals were found, and endocrine and biochemical evaluations excluded hypercortisolism and hyperaldosteronism. Urinary metanephrine and normetanephrine/creatinine ratios were elevated, compatible with a diagnosis of pheochromocytoma. Symptomatic treatment with phenoxybenzamine was started and resulted in normalisation of a systolic blood pressure and reduction of arrhythmias. However, the onset of anorexia, vomiting and clinical deterioration prompted exploration of the adrenocortical reserve through an adrenocorticotropic hormone stimulation test, which confirmed glucocorticoid deficiency. Mineralocorticoid deficiency was ruled out by normal plasma aldosterone concentration and renin activity. Finally, an elevated endogenous plasma adrenocorticotropic hormone concentration defined the primary origin of the hypocortisolism. Clinical resolution occurred with prednisolone supplementation. This is the first report of hypocortisolism in a dog caused by a bilateral pheochromocytoma.