Plays a role as a glutathione (GSH)-dependent antioxidant. May be involved in a redox-related process. May play a role in the myopathies of selenium deficiency (By similarity). Expressed ubiquitously with predominant expression in the pituitary, spinal cord, sciatic nerve, cerebral cortex, cerebral nuclei, thalamus, cerebellum, muscle, cartilage, trachea, gizzard and artery. Weakly expressed in pancreas, testis, ovary, kidney and veins. Up-regulated by dietary selenium in cerebral tissue. Belongs to the SelWTH family. Selenoprotein W subfamily.