However, mutations in DUOX2, the NADPH oxidase that generates hydrogen peroxide (H2O2) essential for organification of iodide, and its accessory protein DUOXA2 are also likely contributors, and the incidence of DUOX2/DUOXA2 mutations in borderline CH has not been fully evaluated in a large cohort (9–11). This evidence concerns the gene DUOX2 and cyclic hematopoiesis.