A 31-year-old female presented with menstrual irregularities, weight gain and hirsutism.
She was recently diagnosed with type 2 diabetes requiring Metformin therapy.
Investigations: Serum cortisol levels failed to suppress on overnight dexamethasone suppression test (ODST) and low dose dexamethasone suppression tests (LDDST) (ODST: unsuppressed cortisol at 343 nmol/l, LDDST 48 h post dexamethasone cortisol of 397 nmol/l). The serum cortisol showed <50% suppression from basal value on high dose dexamethasone suppression test (HDDST) (6945 nmol/l). ACTH levels were ranging between 66 (0900 h) and 47 (midnight). Her 24 h urinary cortisols were elevated with values between 850 and 1000 nmol/24 h (normal range <250 nmol/24 h). Rest of the baseline pituitary hormone profile was normal.
MRI pituitary showed a 4 mm micro adenoma in the left lateral wing of the gland.
In view of concordant clinical, biochemical and radiological results, diagnosis of Cushings disease was made.
Treatment: She was initially commenced on Metyrapone 250 mg tds. The pituitary adenoma was extirpated by transphenoidal surgery. Histology confirmed normal adenohypophysis and neurohypophysis with extensive immunoreactivity to GH and ACTH.
Follow up: Postoperative glucagon stimulation test confirmed inadequate ACTH reserve with peak cortisol of 176 nmol/l. GH reserve was adequate with no evidence of acromegaly.
Post operative MRI pituitary was normal.
Her diabetes mellitus reversed to impaired glucose tolerance test.
Two years post surgery, confirms remission with no biochemical or radiological evidence of recurrence.
Her recent glucagon stimulation test is now suggestive of inadequate GH reserve (peak GH 1.24 μg/l).
Conclusion: Our case illustrates a rare presentation of Cushings disease due to a dual staining pituitary adenoma. At the same time, it also raises the question of safety of treating such a case with GH replacement therapy.