In neonates, which type of bilirubin is less likely to be bound to albumin?

In neonates, indirect bilirubin is less likely to be bound to albumin. Understanding bilirubin metabolism is essential in neonatology. Bilirubin exists in two primary forms: direct (conjugated) and indirect (unconjugated) bilirubin.

Indirect bilirubin is the form that is not water-soluble and requires binding to albumin for transport in the bloodstream. In neonates, several factors contribute to the lower levels of albumin binding available for indirect bilirubin. One of the critical factors is the relatively lower concentration of serum albumin in newborns compared to older children and adults. Additionally, the immature liver function in neonates can result in a decreased ability to conjugate bilirubin effectively, leading to an accumulation of indirect bilirubin in the blood.

The presence of free bilirubin, while relevant, is specifically a subset of indirect bilirubin that remains unbound and is considered toxic. Thus, this type is particularly pertinent when discussing the risk of kernicterus, a serious condition resulting from high levels of unbound bilirubin affecting the central nervous system.

In contrast, direct bilirubin is water-soluble and is readily excreted in bile, so binding to albumin is less of a concern for