Congenital Adrenal Hyperplasia Caused by 21-Hydroxylase Deficiency By Andrew Calabria, MD, The Children's Hospital of Philadelphia Reviewed / Revised Aug 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Key Points Topic Resources Body Surface Area (Du Bois... Adrenal hormone synthesis 21-Hydroxylase (CYP21A2) deficiency causes defective conversion of adrenal precursors to cortisol and, in some cases, to aldosterone, sometimes resulting in severe hyponatremia and hyperkalemia.