Used in clinical and research laboratories to quantitatively measure levels of human cytochrome P450c21A (21-hydroxylase) in biological samples such as serum, plasma, or cell culture supernatants. This ELISA kit is particularly valuable in studies related to autoimmune adrenal diseases, including Addison’s disease and autoimmune polyendocrine syndromes, where autoantibodies against 21-hydroxylase are biomarkers. It enables early detection of autoimmune responses targeting the adrenal cortex, supports diagnosis of congenital adrenal hyperplasia (CAH) in research settings, and aids in monitoring disease progression or immune activity in at-risk individuals. The assay is also used in immunological research to investigate the role of 21-hydroxylase in autoimmunity and to evaluate immune responses in type 1 diabetes and other associated autoimmune conditions.