Haptoglobin
DefinitionThis is a test that measures the amount of haptoglobin, a protein that binds free hemoglobin, in blood.
Why is the Test Performed?
Haptoglobin is measured to assess the rate at which your red blood cells are being destroyed. When red blood cells die, a process called hemolysis, they release their hemoglobin.
The liver produces haptoglobin and secretes it into the blood, where it finds and attaches to any "free" hemoglobin -- that is, hemoglobin not contained within red blood cells. The concentration of free hemoglobin is ordinarily very low, but the level rises whenever red blood cells are being destroyed.
After haptoglobin attaches to hemoglobin, the molecule goes to the liver where its components (iron, heme, and amino acids) are recycled. This process destroys the haptoglobin. When red blood cells are actively being destroyed, the rate of haptoglobin destruction by the liver will outpace the rate at which new haptoglobin is created. Thus, the levels of haptoglobin in the blood will decrease.
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