Q. A 45-year-old man has presented to the medical outpatient department with complaints of excessive fatigue, muscle weakness, and unexplained weight gain. He mentions he has been gaining weight, mostly around the abdomen and face. His wife also noticed that his skin appeared thinner, with bruising easily. On physical examination, the physician observed a "moon face," central obesity, and purple striae on his abdomen. Blood tests show elevated levels of cortisol even after a dexamethasone suppression test. What is the most appropriate next step in the management of this patient?