Presumptive iatrogenic hypoadrenocorticism induced by high-dose ketoconazole administration in a dog

A 11-year-old male neutered Shih Tzu was referred to a tertiary facility with a history of weight loss, decreased appetite, polydipsia, and lethargy. The dog had a 10-year history of nonspecific allergic dermatitis and was being treated with 16 mg/kg of ketoconazole q12h for Malassezia dermatitis. Vague gastrointestinal signs, hypocholesterolemia, and lack of a stress leukogram increased suspicion for hypoadrenocorticism (HA). An adrenocorticotropic hormone (ACTH) stimulation test identified hypocortisolemia on pre- and post-ACTH samples and ketoconazole was discontinued. After a short course of corticosteroid treatment, an ACTH stimulation test was repeated and pre-ACTH cortisol concentration was within the reference range, and the post-ACTH cortisol concentration was mildly increased. The temporal association between return of adequate adrenocortical cortisol production and discontinuation of ketoconazole led to the conclusion that the dog had developed iatrogenic HA secondary to ketoconazole treatment.