GFER (growth factor, augmenter of liver regeneration) is a FAD-dependent sulfhydryl oxidase functioning as a critical regulator of mitochondrial redox homeostasis. The protein exists in multiple isoforms: long forms localized to the inner mitochondrial space cooperate with Mia40 to ensure proper protein folding during mitochondrial protein import, while short cytosolic forms exhibit anti-apoptotic and anti-oxidative properties 1. GFER operates within the CHCHD4/GFER disulfide relay system in the mitochondrial intermembrane space, where it maintains intracellular iron homeostasis through interaction with PCBP1 and supports PINK1 accumulation necessary for mitophagy 2. Beyond its classical liver regeneration function, GFER demonstrates tissue-specific roles in disease regulation: in ulcerative colitis, GFER downregulation promotes ferroptosis in intestinal epithelial cells, while GFER overexpression inhibits ferroptosis markers and alleviates inflammation 3. In pancreatic adenocarcinoma, GFER depletion disrupts redox homeostasis and stimulates anti-tumor immunity via the cGAS-STING pathway 4. Loss-of-function GFER mutations cause mitochondrial encephalomyopathy with congenital cataracts, hearing loss, and developmental delay 5. A GFER polymorphism (rs1046495) confers protective effects against type 2 diabetes by optimizing ROS levels in the electron transport chain 6. GFER also associates with idiopathic pulmonary fibrosis pathogenesis 7. These findings establish GFER as a multifunctional mitochondrial protein with therapeutic implications across inflammatory, neoplastic, and metabolic diseases.