Reduces thioredoxin, the e− donor for peroxiredoxin reduction of H2O2 and other peroxides. Using flavin adenine dinucleotide (FAD) as a coenzyme, it catalyzes the reduction of thioredoxin (Trx) by NADPH. It participates in various cellular processes, including DNA synthesis, protein folding, and cell signaling, and is implicated in several diseases, including cancer and neurodegenerative disorders. The gene discussed is TXN; the disease is cancer.