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home - Liver - Bilirubin Metabolism - Gilberts Syndrome Written by Dr Sebastian Zeki

Gilberts Syndrome

Gilbert's syndrome UGT1A1 promoter TATAA is 7TAA instead of 6TAA (in normals) ...Reduced produc-tion UGT1A1 to 30% of normal -9 % homozygous /30 % heterozygous.-Not all homozy-gotes get hyperbili-rubin and in Japan other genes are implicated-Autosomal recessive Usually diag-nosed in young adult males (higher bilirubin in males and puberty increases bilirubin levels Bilirubin usually < 3 mg/dL and can be normal.Can be higher in1.Fasting- Bilirubin inc x3 within 48 hours once daily calories <400kcal/day or normocaloric without lipidsNormalises in 24 hours once normal dietMay be due to release of bilirubin contained within adipocytes, decreased conjugation due to depletion of UDP-GA (which serves as a cosubstrate in glucuronidation), and enhanced cycling of bilirubin by the enterohepatic circulation.2.Fever, physical exertion or stress.3.3 hrs after iv nicotinic acid (inc bilirubin formation in spleen and enhanced uptake in liver).4.A relationship to menses has been reported in two women.Can be low in:Corticosteroids (inc hepatic uptake of bilirubin), or hepatic enzyme inducers (such as phenobarbital and clofibrate)-normalize [plasma bilirubin] within 1-2 wks Clinical significance —It is benign.There are no complications.A mild, chronic hyperbilirubinemia may be antioxidant (inverse assoc between [bilirubin] and hx of cancer.Patients may be more susceptible to toxic drugs and inadequate glucuro-nidation (eg acetaminophen and tolbutamide) - only reported for irinotecan (active metabolite SN-38 glucuronidated in the liver).Patients can get major diarrhoeal episodes as a result of non-glucuronidation. Histological Features:Centrilobular lipofuscin pigment- otherwise it is normal.Minor abnormalities can be seen at electron microscopy. Treatment —No specific therapy required. Diagnosis If have mild isolated unconjugated hyper-bilirubinaemia, can assume its Gilbert’s. Determinants of plasma [bilirubin] — Written by Dr Sebastian Zeki

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