A 42 year old woman presents with oligomenorrhea for 2 years, and 30 kg of weight gain during the same period, even though her diet remained unchanged. Her medical history is significant for type 2 diabetes, hypertension and dyslipidemia for 3 years; while well controlled initially, these have worsened over the last year. She is currently on Metformin, Gliclazide, Telmisartan, and Rosuvastatin. Her family history is significant for polycystic ovarian disease in a sister. She only drinks socially and does not smoke. A full blood count is within normal parameters, as are serum electrolytes, and renal and liver profiles. A thyroid profile and serum FSH, LH, testosterone, and growth hormone levels are also normal.
Post dexamethasone serum cortisol level: 170 nmol/L (< 50) The test is repeated; the new value is 155 nmol/L
24-hour urinary free cortisol: 210 nmol/24h (55-250) A repeat test is performed; the new value is 180 nmol/24h
ACTH level: 4 pg/mL (9-52)
The MRI scan reveals a homogeneous hypodense mass measuring 5.1 × 3.7 cm in the superior aspect of the left adrenal gland. No other abnormalities are detected.