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Adrenocorticotropic hormone is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress. Its principal effects are increased production and release of cortisol by the cortex of the adrenal gland. ACTH is also related to the circadian rhythm in many organisms.
Deficiency of ACTH is an indicator of secondary adrenal insufficiency or tertiary adrenal insufficiency ]. Conversely, chronically elevated ACTH levels occur in primary adrenal insufficiency when adrenal gland production of cortisol is chronically deficient. In Cushing's disease a pituitary tumor is the cause of elevated ACTH and an excess of cortisol – this constellation of signs and symptoms is known as Cushing's syndrome.