126 Transferrin (TFN)
Transferrin is the main iron-transport protein in blood. It is made by the liver and can carry two atoms of ferric iron. Loaded transferrin binds to transferrin receptors on cells, especially developing red cells in the bone marrow, and is taken up; in the acidic interior of the cell the iron is released. When iron stores are low, the liver produces more transferrin; when stores are high or in inflammation, it produces less. The proportion of transferrin binding sites occupied by iron is the transferrin saturation.
Clinical significance
Low transferrin
Anaemia of inflammation (chronic infection, autoimmune disease, cancer), iron overload (haemochromatosis), liver disease, protein loss (nephrotic syndrome), malnutrition. Transferrin is also a marker of nutritional status.
High transferrin
Iron deficiency (blood loss, poor intake or absorption), pregnancy, oestrogen-containing medicines. In iron deficiency, transferrin and TIBC rise while serum iron, saturation and ferritin fall.
Very high transferrin saturation (for example above about 45% fasting) suggests iron overload and should be followed by ferritin and, if indicated, genetic testing for haemochromatosis.
Fatigue, pallor, breathlessness, brittle nails or cravings for ice may indicate iron deficiency; its cause (for example bleeding from the gut or heavy periods) must be found.
References
This article is for general information and does not replace a consultation with a doctor. Laboratory results must be interpreted by a physician together with symptoms and other tests.
Published on 12 May 2024