Haptoglobin

Haptoglobin is a protein produced by the liver. It binds to hemoglobin in the blood, which is then removed by the spleen. The haptoglobin-hemoglobin complex is a way for the body to recover the iron contained in the hemoglobin, preventing it from being lost in the urine. Haptoglobin levels are decreased in hemolytic anemia and increased in inflammation or after tissue damage.

Function

Haptoglobin is a glycoprotein that binds free hemoglobin released from erythrocytes with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen).

In clinical settings, the haptoglobulin assay is used to screen for and monitor intravascular hemolytic anemia. In this condition, the haptoglobin levels will be very low.

Structure

Haptoglobin is composed of two alpha and two beta chains; the alpha chains are connected by disulfide bonds. The haptoglobin monomer consists of a "head" domain and a "leg" domain. The head domain binds hemoglobin, while the leg domain is responsible for dimerization.

Clinical significance

Haptoglobin levels can be tested in a simple blood test. Haptoglobin is decreased in conditions that feature intravascular hemolysis, such as sickle cell disease, thalassemia, malaria, and autoimmune hemolytic anemia. It is also decreased in liver disease, as it is produced by the liver.

Haptoglobin is increased in conditions featuring tissue damage and/or inflammation, such as burns, trauma, surgery, and cancer.

See also

• Hemoglobin
• Hemolysis
• Anemia
• Sickle cell disease
• Thalassemia
• Malaria
• Autoimmune hemolytic anemia
• Liver disease
• Burns
• Trauma
• Surgery
• Cancer

Haptoglobin

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