This test measures the level of adrenocorticotropic hormone (ACTH) in the blood. ACTH is a hormone made by the pituitary gland, a small gland at the base of the brain. ACTH controls the production of another hormone called cortisol. Cortisol is made by the adrenal glands, two small glands located above the kidneys. Cortisol plays an important role in helping you to: Respond to stress Fight infection Regulate blood sugar Maintain blood pressure Regulate metabolism, the process of how your body uses food and energy Too much or too little cortisol can cause serious health problems.