Excessive activity of the adrenal gland which causes excessive production of one or more adrenal hormones (aldosterone, corticosteroids, androgenic steroids, epinephrine and norepinephrine). The increased adrenal gland activity may be caused by an adrenal gland tumor or by excessive stimulation of the gland. Pituitary hormones stimulate adrenal gland activity. See also Adrenal gland hyperfunction