 The product solubility in blood is increased allowing it to be eliminated from the body by the kidneys.A deficiency in the bilirubin specific form of glucuronosyltransferase is thought to be the cause of Gilbert's syndrome, which is characterized by unconjugated hyperbilirubinemia.It is also associated with Crigler–Najjar syndrome, a more serious disorder where the enzyme's activity is either completely absent (Crigler–Najjar syndrome type I) or less than 10% of normal (type II).