The thioredoxin reductase (TrxR) family is a group of selenium-containing enzymes responsible for reducing thioredoxins (Trx), regulating redox status and signal transduction. TrxR is localized in both the cytoplasm and mitochondria, including TrxR1 (cytoplasmic) and TrxR2 (mitochondrial), and is involved in antioxidant defense, cell proliferation, death, and immune response. By reducing Trx, TrxR affects various biological processes such as DNA synthesis and repair, and cell signaling. Gene expression is strictly regulated, and the tissue-specific expression pattern is associated with tissue types. Mutations or dysregulation of expression are associated with health issues such as cancer, cardiovascular diseases, and neurodegenerative diseases, making TrxR a potential therapeutic target.