Abstract
Cushing syndrome is a disorder that occurs when the body is exposed to a higher than normal level of the hormone cortisol. It is most commonly caused by exogenous glucocorticoids, and less commonly due to endogenous sources. Ectopic adrenocorticotropic hormone (ACTH) syndrome is one of the rare causes of endogenous Cushing syndrome engendered by oversecretion of ACTH from a tumor outside of the pituitary or adrenal glands. We present a case of a 74-year-old male with uncontrolled type 2 diabetes mellitus who was suspected of having Cushing syndrome on chest CT due to increasing mediastinal lipomatosis and enlarging bilateral adrenal glands. Cushing syndrome was confirmed based on clinical features and biochemical tests. Further investigation revealed an ACTH-producing functional neuroendocrine tumor of the pancreas causing ectopic Cushing syndrome.