Review Article
Selenium and Thyroid Disease: From Pathophysiology to Treatment
Table 3
Main groups of selenoproteins found in the thyroid gland and their function [
1,
2].
| Glutathione peroxidase | GPX | Catalyzes the reduction of H2O2 and protects against oxidative stress |
| Cytosolic GPx 1 | GPX1 | Antioxidative defense | Gastrointestinal GPx 2 | GPX2 | Antiapoptotic function in colon crypts; helps to maintain intestinal mucosal integrity | Extracellular GPx 3 | GPX3 | Antioxidant in extracellular fluid; thyroid protection from hydrogen peroxide in thyrocytes and follicular lumen | Phospholipid GPx 4 | GPX4 | Reduces the phospholipids’ hydroperoxides; regulates apoptosis |
| Iodothyronine deiodinase | DIO | Production of active thyroid hormone T3, reverse T3 (rT3), and T2 |
| Type I DIO | DIO1 | Conversion of T4 to T3 | Type II DIO | DIO2 | Local production (intracellular) of T3 from T4 | Type III DIO | DIO3 | Production of rT3 from T4 and T2 from T3 |
| Thioredoxin reductase | TXNRD | Oxidoreductase activity having NADPH as a cofactor |
| TXNRD cytosolic | TXNRD1 | Main antioxidant at the cellular level | TXNRD mitochondrial | TXNRD2 | Regulates cell proliferation |
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