Transferrin

The transferrin test (iron carrier, siderophilin) is used to assess iron homeostasis and body iron stores when interpreted with serum iron and total and unsaturated iron‑binding capacity to derive transferrin saturation. These results support distinction of iron deficiency anemia from anemia of chronic disease. Transferrin also functions as an indicator of hepatic synthetic capacity and protein‑energy nutritional status. Values are typically increased in iron deficiency and decreased with chronic inflammation, hereditary atransferrinemia, acquired liver disease, neoplastic processes, and renal disease.

Transferrin is synthesized by the liver and circulates to shuttle dietary and recycled iron to tissues such as the liver and spleen. Under physiologic conditions, approximately one-third of its iron‑binding sites are occupied; the unoccupied fraction reflects iron availability and is captured by total and unsaturated iron‑binding capacity and the derived transferrin saturation. Because the concentration depends on hepatic synthetic function and protein intake, serum transferrin decreases with liver synthetic impairment and with inadequate nutrition or malabsorption. In severe protein‑energy malnutrition, transferrin may fail to increase despite concurrent iron deficiency.