A 35-year-old woman presents with fatigue, weakness, and weight gain. Her blood pressure is 155/90 mm Hg, pulse 80/min, and there is central obesity with skin striae. Investigations are shown in Table given below. Which of the following is the most likely diagnosis?Table given below is the case work-up NormalPatientPlasma ACTH pg/mL< 150< 50Plasma cortisol m/dL1735Urine 17-OH mg/24 h2 to 1025Urine 17-Ks mg/24 h5 to 1510Urine 17-OH response to:ACTH IVIncreasex5No responseDexamethasone 0.5 mg< 3.0No response2.0 mg< 3.0No responseMetyrapone 750 mgIncreasex 2No responseAbbreviation: ACTH--adrenocorticotropic hormone