MSRA-0518

MSRA-0518

A 35-year-old woman presents to the Endocrinology Clinic with bruising, striae, acne and hirsutism.
On examination, the patient appears lethargic and depressed, with centripetal obesity and demonstrable proximal myopathy. Her blood pressure is 165/106 mmHg
Investigations reveal the following:
Investigation Result Normal values
Sodium (Na+) 136 mmol/l 135–145 mmol/l
Potassium (K+) 2.8 mmol/l 3.5–5.0 mmol/l
Random glucose 8.2 mmol/l 3.9–7.1 mmol/l
A low-dose dexamethasone test and a 24-hour urinary cortisol test are ordered.
Which of the following is the most common cause of Cushing syndrome?