The most common cause of Cushing's syndrome (CS) is iatrogenic (administration of exogenous steroids).
This can be caused by a tumor of the adrenal glands, the lungs, or the pituitary gland. When the tumor produces too much ACTH, it causes over production of cortisol by the adrenal glands. If the source is the pituitary, it is called Cushing's disease 2)
Expert opinion and a consensus statement on Cushing syndrome (CS) indicate that, in a patient with a clinical presentation and biochemical studies consistent with a pituitary etiology, the presence of a pituitary tumor ≥6 mm is highly suggestive of Cushing disease (CD).
This is most often as a result of Pituitary corticotroph adenoma.
Definite treatment of Cushing's syndrome is surgical removal of ACTH-secreting lesion and prerequisite for this surgical management requires localization of ACTH-secreting source 3).