Gilbert's syndrome is an inherited disorder that causes a chronic, intermittent hyperbilirubinemia due to increased unconjugated (indirect) bilirubin. It is associated with defective transport and conjugation of unconjugated bilirubin within hepatocytes. It is fairly common, affecting 3-7% of the general population.


Inheritance: autosomal dominant with incomplete penetrance


Basis: impaired hepatic UDP-glucuronosyl transferase activity, but present


Most patients are identified during adolescence or as a young adult, due to either jaundice or an elevated serum bilirubin concentration. The patients are often asymptomatic, but some may experience fatigue, malaise or nonspecific symptoms.


Bilirubin findings:

(1) intermittent hyperbilirubinemia, with at least 2 occasions over 6 months

(2) no bilirubinuria

(3) conjugated (direct) bilirubin represents < 20% of the total bilirubin



(1) no evidence of liver disease (normal GGT, transaminases, albumin, prothrombin time and liver biopsy)

(2) no evidence of hemolysis (normal serum hemoglobin, reticulocyte count, haptoglobin, and blood smear morphology)


NOTE: Because of the frequency of Gilbert's syndrome, a patient may have it together with a common liver or hematologic condition. Diagnosis of the Gilbert's syndrome then requires evaluation after recovery from the other condition.


Increases in total bilirubin may follow:

(1) caloric restriction (fasting with < 400 calories a day for 72 hours causes increases in serum unconjugated bilirubin in 100% of patients)

(2) carbohydrate load

(3) nicotinic acid

(4) physical exercise

(5) stress

(6) febrile illness

(7) menstruation or pregnancy

(8) birth control pills

(9) alcohol


Decrease in total bilirubin may follow:

(1) return to a normal diet after fasting

(2) administration of phenobarbital or other liver enzyme inducing agents

(3) administration of prednisone


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