TPO and thyroid cancer: In the thyroid gland, DUOX2 contributes mainly to thyroid hormone synthesis by providing H2O2 to thyroid peroxidase (TPO), while ROS-generating NADPH oxidases DUOX1 and NOX4 are associated with oxidative DNA damage that could promote thyroid radio-carcinogenesis and oncogenes thyroid cancer dedifferentiation, respectively [17,27,33,34,35].