D i.e Liver parenchymal disease Haptoglobin (Hp) binds extracorpuscular (i.e. extracellular) hemoglobin (Hb), preventing free Hb from entering the kidney. Hp-Hb complex is removed from plasma by haptocytes. Levels of haptoglobin falls rapidly in situations where hemoglobin is constantly being released from RBC such as occurs in hemolytic anemia (haemorrhage). But in case of parenchymal liver disease, Hp-Hb complex removal is deranged so reduction in haptoglobin level is masked. Haptoglobin It is a plasma glycoprotein that binds extracapsular hemoglobin (Hb) in a tight non-covalent complex. Its amount ranges from 40mg- 180 mg of hemoglobin binding capacity / deciliter. Only 10% of degraded hemoglobin is released in circulation (i.e. extra corpuscular) the remaining 90% is present in old damaged RBCs, which are degraded by histiocytic system. Free Hb (molecular mass 65KDa) passes through glomerulus and precipitate in tubules. However, after binding with haptoglobin (90 KDa) the Hb-Hp complex (155KDa) becomes too large to pass through glomerulus. So the function of haptoglobin is to prevent loss of free hemoglobin into kidney and conserve the valuable iron present in hemoglobin, which would otherwise be lost to the body. Humans have 3 polymorphic forms, k/a Hp 1-1, Hp 2-1, Hp 2-2. Low levels of haptoglobins are found in patients with hemolytic anemia. This is explained by the fact that where the life of Hp is 5 days, the t1/2 of Hb-Hp complex is 90 minutes, the complex being rapidly removed by hepatocytes. So when the hepatoglobin is bound to Hb, it is cleared from plasma about 80 times faster than normally. Hb is an acute phase protein & is elevated in variety of inflammatory states. * Haptoglobin related protein binds hemoglobin; hemopexin binds free heme; and albumin binds metheme (ferric heme)