The causes of low unsaturated iron binding are: decreased synthesis of transferrin (Tf), loss of transferrin, and iron deficiency. Under normal circumstances, serum iron can only bind to 1/3 of Tf, 2/3 of Tf fails to bind, and the Tf that cannot bind to iron is called unsaturated iron binding capacity. 1. Reduced synthesis of transferrin (Tf): transferrin is mainly synthesized by liver cells. When cirrhosis, chronic liver injury and other diseases occur, liver cells are destroyed, resulting in reduced synthesis and release of transferrin, and a corresponding reduction in transferrin that is not bound to iron, leading to low unsaturated iron binding capacity. 2. Transferrin loss: the epithelial cells, endothelial cells and basement membrane of the glomerular dirty layer constitute the filtration membrane, and the charge barrier and filtration membrane can effectively prevent the passage of protein and other macromolecules, and maintain the osmotic pressure and electrolyte balance of the body. In nephrotic syndrome, the filtration membrane is destroyed, and transferrin is lost in large quantities through the kidneys, leading to a decrease in the binding capacity of unsaturated iron. 3. Iron deficiency: Liver disease, chronic inflammation and peptic ulcer lead to a large amount of iron loss, the body according to the serum iron content of transferrin production is reduced accordingly, resulting in a reduction in the synthesis of total transferrin, unsaturated iron binding capacity is reduced. When the unsaturated iron binding capacity is reduced, it is recommended that patients go to regular hospitals for systematic examination, early detection of the disease and treatment.