Cushing's syndrome refers to the manifestations induced by chronic exposure to glucocorticoid excess and may result from various causes that are all associated with tumors. The most frequent one, that which was first recognized by Harvey Cushing (Cushing 1932) – and therefore called Cushing's disease – is due to adrenocorticotropin (ACTH) hypersecretion by a pituitary corticotrope adenoma; the ectopic ACTH syndrome is another, much rarer (∼5-10%) one, caused by a variety of so-called ACTH-secreting non-pituitary tumors; finally, approximately 30% of Cushing's syndromes are ACTH-non-dependent, caused by primary adrenocortical tumors, most often unilateral and either benign or malignant.
The first case of ectopic ACTH syndrome was probably reported by Brown (1928) who described the case of a bearded woman with diabetes. At that time the author had no idea that ACTH existed. The discovery of ACTH, the development of an ACTH bioassay, and the pioneering work of Liddle's group eventually led