Cushing syndrome is caused by prolonged exposure to elevated levels of
either endogenous glucocorticoids or exogenous glucocorticoids.
Endogenous glucocorticoid overproduction or hypercortisolism that is
independent of ACTH is usually due to a primary adrenocortical neoplasm
(usually an adenoma but rarely a carcinoma). Bilateral micronodular
hyperplasia and macronodular hyperplasia are rare causes of Cushing