A 40-year-old woman presents with easy fatigability, weakness, lethargy, and poor concentration for 10 months. She also complains of a weight gain of 9 kg over the last 6 months, which she believes has mainly affected her abdomen and neck. She was recently diagnosed with impaired glucose intolerance but is currently not on any medications or dietary modifications. She is a mother of two boys. Her periods are irregular and have occurred 6 times in the last 10 months, with the most recent period being six weeks ago. A urine pregnancy test is negative. A complete blood count is found to be within normal parameters.
Following overnight dexamethasone suppression, serum cortisol levels are 2.4 mcg/dL (normal: <1.8)
24-hour urinary cortisol excretion is 204 mcg/day (normal: <50)
Basal ACTH is 120 pg/mL and 113 pg/mL on two consecutive days (Normal: 9 - 52)
Gadolinium-enhanced MRI reveals an 8 mm diameter hypointense mass on the right side of the pituitary gland, suggestive of a microadenoma. The pituitary stalk is deviated towards the left.