A 52-year-old man with a 3-month history of hypertension, proximal myopathy, and weight gain undergoes investigation for suspected Cushing syndrome. His 24-hour urinary free cortisol is elevated at 250 μg/24h (normal <50), and plasma ACTH is 8 pg/mL (normal 10–50). High-dose dexamethasone suppression test (HDDST) shows no suppression of cortisol. Which of the following is NOT consistent with the diagnosis of adrenocorticotropic hormone (ACTH)-independent Cushing syndrome?