ACTH (adrenocorticotropic hormone) is a hormone produced by the
pituitary gland, located below the brain. ACTH activates glands on the kidneys
(adrenal glands) to make cortisol, a substance that helps the body deal with
stress.
When cortisol levels in the blood rise, the ACTH levels in a
healthy person normally fall in response. When cortisol levels decrease, ACTH
levels normally rise.