DUOX2 and cyclic hematopoiesis: Hulur et al. (44) reported that a CH child with goiter lacked one allele of DUOX2 and DUOXA1, with loss of function of DUOXA2. We demonstrated for the first time that DUOX2 and DUOXA1, as members of the NADPH oxidase family that were once thought to be involved only in thyroid hormone synthesis (35, 45), may play a role in thyroid development.