According to the origin of the hypercortisolism, endogenous CS can be also differentiated into an ACTH-dependent form resulting from ACTH-secreting pituitary neuroendocrine tumours (Cushing’s disease, CD) or ACTH-and or corticotropin releasing hormone (CRH) secreting neuroendocrine tumours outside the hypothalamic-pituitary area (ectopic Cushing syndrome, ECS), and an ACTH-independent form of adrenal origin (adrenal Cushing’s syndrome, ACS) (adenoma, carcinoma or bilateral adrenal hyperplasia). This evidence concerns the gene CRH and neuroendocrine neoplasm.