An acute-phase plasma protein found in human plasma at 100-300 mg per 100 ml. Binds hemoglobin, thus preventing loss of iron through the kidneys. Humans are polymorphic for haptoglobin, with three major phenotypes: Hp 1-1, Hp 2-1, and Hp 2-2. While the phenotypic distribution can vary greatly between ethnicities and geographic location, the Hp 2-1 phenotype is the most prevalent phenotype in humans. Plasma concentrations of haptoglobin are highest in individuals with Hp 1-1, intermediate in Hp 2-1 individuals, and lowest in Hp 2-2 individuals. Hp 1-1 is the most effective at binding hemoglobin, and Hp 2-2 is the least effective. This functional difference may be associated with the frequency and severity of epilepsy attacks, as researchers