Adrenocorticotropic hormone (ACTH) is a polypeptide hormone thatstimulates adrenocortical activity. It is produced by the prohormoneproopiomelanocortin (POMC), which is synthesized in the corticotroph andmelanotroph cells found in the intermediate and anterior lobe of the pituitarygland and the arcuate nucleus of the hypothalamus. ACTH is also synthesized inthe skin. It plays a role in controlling steroidogenesis in the adrenal glandand prevents reactive oxygen species (ROS)-induced cell toxicity. Higher levelsof ACTH lead to skin hyperpigmentation due to the hyperstimulation ofmelanocytes, characteristic of primary adrenal insufficiency (PAI). Deficiencyof ACTH synthesis, receptors, or signaling is associated with adrenalinsufficiency.