Hyperbilirubinemia is primarily characterized by the elevation of what in the serum?

Hyperbilirubinemia is primarily characterized by an elevation in unconjugated serum bilirubin concentrations. This condition often occurs due to increased production of bilirubin, which can be a result of hemolysis, or decreased conjugation, as seen in certain liver diseases.

Unconjugated bilirubin is the form that is not yet processed by the liver and is typically poorly soluble in water, which means it does not get easily excreted. In conditions leading to hyperbilirubinemia, such as hemolytic anemia or Gilbert's syndrome, the liver may be unable to keep up with the production of bilirubin, leading to accumulation of unconjugated bilirubin in the bloodstream.

Total bilirubin concentrations include both conjugated and unconjugated bilirubin, but the defining feature of hyperbilirubinemia, especially in many clinical settings, is specifically the rise in unconjugated bilirubin. This differentiates it from other conditions where conjugated bilirubin or direct bilirubin might be elevated instead, such as in cases of liver obstruction or liver disease where the liver is unable to adequately process or excrete bilirubin. Therefore, focusing on the elevation of unconjugated serum bilirubin is key to understanding the underlying conditions related to