Is it Possible to Have Coexisting Exogenous and Endogenous Cushing's Syndrome?

The coexistence of exogenous and endogenous Cushing's syndrome is exceptionally rare. Here, we report the case of a 40-year-old female patient who had been self-medicating with dexamethasone for three years and who presented with asthenia and abdominal pain ten days after discontinuing corticosteroid therapy. The initial clinical suspicion was adrenal insufficiency following corticosteroid withdrawal; however, the patient's 8 a.m. serum cortisol level was elevated at 46 µg/dL. The possibility of concomitant endogenous Cushing's syndrome was therefore considered. Hormonal investigations confirmed adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome, and magnetic resonance imaging of the pituitary region revealed a pituitary macroadenoma measuring 14 × 15 × 12 mm. The patient underwent transsphenoidal surgery with an uneventful postoperative course. Hormonal evaluation should be considered in patients receiving prolonged corticosteroid therapy when clinical manifestations persist after corticosteroid withdrawal, particularly in the presence of persistent hypercortisolism or absence of expected hypothalamic-pituitary-adrenal axis suppression.