Elevated ACTH levels indicate a disorder in the body's cortisol production or balance. This condition can lead to increased cortisol levels due to overstimulation of the adrenal glands (e.g., Cushing's disease). Conversely, if the adrenal glands produce insufficient cortisol, the body may increase ACTH secretion as a compensatory response (e.g., Addison's disease). Hypopituitarism is typically characterized by low ACTH levels.