- High glucose level caused increase in extra- and intracellular H2O2 pro-duction in thyrocytes through activation of the PKC pathway.- Upregulation of DUOX1 and NOX4 via activation of PKC and reduced TPO mRNA levels. - Insulin in the absence of TSH increased production of H2O2 more than hyperglycemia alone. Here, TPO is linked to Hyperglycemia.