NOX4 and Hashimoto thyroiditis: While defects of this system interfere with thyroid hormone synthesis, another new intracellular ROS generating system has been demonstrated in the human thyroid gland: NADPH oxidase 4 (NOX4) [47]; defects in such a system could be associated with thyroid cancer (via activation by the H-Ras oncongene) and Hashimoto’s thyroiditis (in such a situation an increased extracellular ROS production causes an augmented ICAM-1 expression and cytokine release) [48].