ABSTRACT
Diagnosis of an adrenal tumor without typical clinical signs related to hyperadrenocorticism and elevated alkaline phosphatase is challenging. This report describes a sex hormone-secreting adrenal tumor in a 10-year-old castrated male Shih Tzu evaluated through repetitive ultrasonographic examination. An adrenocorticotropic hormone stimulation test revealed elevated concentrations of androstenedione and 17-hydroxyprogesterone but a normal cortisol concentration. A mass was surgically excised and adenoma was diagnosed histopathologically. In the present case, adrenal tumor was strongly suspected based on a gradual increase in adrenal size and a change from peanut shape to an irregular mass on repetitive ultrasonography. Repetitive ultrasonographic examination of the adrenal gland is recommended when an abnormal ultrasonographic appearance of adrenal gland is identified, even in an asymptomatic dog.