The pituitary hormone adrenocorticotropic hormone or ACTH, is made by the pituitary gland. ACTH regulates the production of cortisol by the adrenal gland. ACTH stimulates the adrenal glands to produce more cortisol.

High levels of cortisol can result from an ACTH producing tumor in the pituitary gland or a cortisol-producing tumor in the adrenal cortex. Cortisol levels in the blood and urine are measured, in order to evaluate the function of the pituitary and adrenal glands.