Population studies on Gilbert's syndrome.

Total serum bilirubin concentration was measured by an Autoanalyzer technique in 197 normal males and 102 normal females. The mean bilirubin concentration was significantly lower in the females than in the males. Total bilirubin concentration in the males showed a bimodal distribution with an antimode at 24 mumol/1 (1.4 mg/100ml). Individuals with bilirubin concentration above this value had unconjugated hyperbilirubinaemia and probable Gilbert's syndrome. Total bilirubin concentration in the females again showed a bimodal distribution with an antimode at 12 mumol/1 (0.7 mg/100ml). It is conceivable that females with bilirubin levels above this also have Gilbert's syndrome. This suggests that the population incidence of Gilbert's syndrome could be as high as 6% and that the sex incidence is approximately equal.