CYP21A2 and primary adrenal insufficiency: For example, Addison's disease in APECED is linked to autoantibodies against steroidogenic P450 cytochrome enzymes, including steroid 21‐hydroxylase (P450c21 or CYP21), expressed in the adrenal cortex, as well as steroid 17‐alpha‐hydroxylase (P450c17 or CYP17) and the side‐chain cleavage enzyme (P450scc or CYP11A1), both of which are expressed in the adrenal glands and gonads [130, 131, 132, 133, 134].