Hyperpigmentation of the skin and mucous membranes is caused by melanocyte-stimulating hormones derived from the adrenocorticotropic hormone (ACTH) precursor proopiomelanocortin, since the lack of negative feedback from cortisol, typical of primary adrenal insufficiency, leads to an augmented secretion of corticotropin-releasing hormone and ACTH [30]. Here, POMC is linked to Adrenal insufficiency.