The protein encoded by this gene is a glycoprotein and a member of the NADPH oxidase family. The synthesis of thyroid hormone is catalyzed by a protein complex located at the apical membrane of thyroid follicular cells. This complex contains an iodide transporter, thyroperoxidase, and a peroxide generating system that includes this encoded protein and DUOX2. This protein is known as dual oxidase because it has both a peroxidase homology domain and a gp91phox domain. Two alternatively spliced transcript variants encoding the same protein have been described for this gene.