The Incidentally Discovered Adrenal Mass

A 68-year-old woman is incidentally found to have a left adrenal mass, 2.8 cm in diameter, on abdominal computed tomography that was ordered to evaluate right lower abdominal discomfort (which has since resolved). Her medical history is notable only for hypertension that has been well controlled with hydrochlorothiazide, at a dose of 25 mg daily. She reports no sweating, palpitations, headache, weight gain, or proximal muscle weakness. Her physical examination is unremarkable. How should she be evaluated?