Cushing's disease is characterized by

Increased serum ACTH and serum coisol * Regardless of etiology all cases of endogenous Cushing's syndrome are due to an increased production of coisol by the adrenal gland. * In most cases, cause is bilateral adrenal hyperplasia due to hypersecretion of pituitary ACTH or ectopic production of ACTH by a nonpituitary source. * The incidence of pituitary-dependent adrenal hyperplasia is three times greater in women than in men. * The primary defect is a pituitary adenoma, as tumor is found in >90% of patients with pituitary-dependent adrenal hyperplasia. * Alternatively, the defect may occasionally reside in the hypothalamus or in higher neural centers, leading to a release of CRH inappropriate to the level of circulating coisol. * This primary defect leads to hyperstimulation of the pituitary, resulting in hyperplasia and tumor formation. * Most individuals with hypersecrete tion of pituitary ACTH are found to have a microadenoma (<10mm) in diameter and macroadenoma (>10 mm). * Traditionally, only an individual who has an ACTH producing pituitary tumor is defined as having Cushing's disease, where Cushing's syndrome refers to all causes of excess coisol: exogenous ACTH tumor, adrenal tumor, pituitary ACTH-secreting tumor, or excessive glucocoicoid treatment.