Although autoimmune destruction of the adrenal gland (sometimes referred to as Addison’s disease) is the most common cause of PAI in adolescents and adults, around 30 single-gene disorders have now been identified that result in PAI through diverse processes, such as impaired development (hypoplasia), blocks in steroid biosynthesis (congenital adrenal hyperplasia, CAH), adrenocorticotropic hormone (ACTH) resistance (familial glucocorticoid deficiency), and metabolic conditions (10–12). This evidence concerns the gene POMC and familial glucocorticoid deficiency.