Cushing syndrome refers to any cause of elevated cortisol concentrations. It is a disorder caused by the body’s exposure to an excess of the hormone cortisol. Cortisol affects all tissues and organs in the body. Pituitary-dependent hyperadrenocorticism (PDH; Cushing disease) is the most common form of hyperadrenocorticism and accounts for 80%-85% of reported cases. Adrenal-dependent hyperadrenocorticism occurs when a unilateral or bilateral adrenal tumor -secretes cortisol and accounts for 10%-15% of cases. Less common causes of hyperadrenocorticism include ectopic secretion of ACTH, episodic Cushing disease, meal induced, and “atypical” manifestations (see: Wikipedia).