When an individual's cortisol levels are low, such as in the case of people with Addison's disease, the hypothalamus region of the brain releases corticotrophin-releasing hormones. This causes the pituitary gland to also secrete another hormone called, adenocortocotropic hormone into the bloodstream. When the adrenal glands detect these hormones, they secrete cortisol, causing blood levels of cortisol to rise.