May act as a redox regulator involved in DUOX proteins folding. The interaction with DUOX1 and DUOX2 suggest that it belongs to a multiprotein complex constituting the thyroid H(2)O(2) generating system. It is however not sufficient to assist DUOX1 and DUOX2 in H(2)O(2) generation. Belongs to the protein disulfide isomerase family. 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.