ACTH (aka corticotropin) is a polypeptide hormone secreted by the anterior pituitary gland
its main actions are to increase synthesis and secretion of corticosteroids from the zona fasciculata of the adrenal cortex (via MC2R ACTH receptor) as part of the biological stress response
ACTH also has a role in bone physiology, especially in osteoblasts
half-life of ACTH in human blood is ~ 10 minutes
impaired secretion of ACTH is a cause of secondary adrenal insufficiency
excessive secretion of ACTH due to a pituitary tumour or ectopic production such as from small cell tumours of lung results in Cushing's syndrome