Soru

A 38-year-old woman is evaluated in the ambulatory setting for recent, unexplained weight gain and new-onset hypertension. Over the past eight months, she has gained $14$ kg despite no changes to her diet or physical activity level. She also reports increasing difficulty climbing stairs and easy bruising on her extremities. Blood pressure is $158/96$ mmHg. Physical examination reveals facial plethora, prominent dorsocervical and supraclavicular fat pads, and broad violaceous striae across the lower abdomen. Initial screening for hypercortisolism is performed using a $1$-mg overnight dexamethasone suppression test. Her serum cortisol level at 8:00 AM the following morning is $14 \mu\text{g/dL}$ (normal: $<1.8 \mu\text{g/dL}$). Which of the following is the most appropriate next step in the diagnostic evaluation of this patient?