17β-Estradiol Stimulates Oxidative Stress Components and Thyroid Specific Genes in Porcine Thyroid Follicular Cells: Potential Differences Between Sexes

17β-estradiol plays a crucial role in regulating cellular processes in both reproductive and non-reproductive tissues, including the thyroid gland. It modulates oxidative stress and contributes to sexual dimorphism in thyroid diseases, with ROS production, particularly H₂O₂, generated by NOX/DUOX enzymes. This study aimed to investigate the effects of 17β-estradiol (10 nM or 100 nM) on the expression of NOX/DUOX, thyroid-specific genes, and endoplasmic reticulum (ER) stress-related genes in male and female porcine thyroid follicular cells. Expression of the studied genes was evaluated by RT-PCR before and after treatment with 17β-estradiol alone or with the addition of NOX4 inhibitor (GKT-136901). Additionally, the level of ROS was measured by flow cytometry analysis. Our results show that 17β-estradiol significantly upregulates thyroid-specific genes, particularly TPO, and stimulates NOX/DUOX expression, affecting the redox state of thyroid cells. It also stimulates ER stress-related genes such as CHOP. In conclusion, estrogen excess may contribute to thyroid disease development via such possible mechanisms as the upregulation of key thyroid-specific genes, particularly TPO, and of genes involved in the cellular response to ER stress, especially CHOP, as well as by the stimulation of the NOX/DUOX system with consequent ROS overproduction. These mechanisms may play a certain role in the higher prevalence of thyroid diseases in women.