What is Gilbert's syndrome?
Gilbert’s syndrome (GS) is a condition in which you have higher than normal amounts of bilirubin in your blood.
The medical name for this is ‘unconjugated hyperbilirubinemia’. It is also sometimes called familial nonhaemolytic bilirubinaemia or constitutional hepatic dysfunction.
These long names may not sound promising but GS is in fact a harmless condition. It is not a disease and it is possible that you may not even know you have it.
GS is usually discovered by chance when a routine or unrelated blood test reveals a rise in the level of bilirubin in your blood. It is likely you will be told that you have high or raised ‘serum bilirubin’.
This is not a bad thing in isolation, but until GS is specifically diagnosed you may be left to worry whether having high bilirubin is an indication of a more serious liver illness.
Although a benign condition, people do report some ill-effects from GS. These may or may not be related to other problems. This section of the website describes some of the symptoms most commonly mentioned and provides advice on how you might avoid these symptoms occurring.
What is bilirubin?
Bilirubin is a normal by-product of the breakdown of old red blood cells. These contain haemoglobin, an important protein that helps transport oxygen around your body. It is also a pigment that gives red blood cells their colour.
Red blood cells last about 120 days. When they expire the haemoglobin is broken down into haem and globin. Globin is a protein that is stored by the body for later use. Haem (or heme) is waste material that needs to be flushed from the body. The ‘pathway’ or removal process that makes this possible is called glucuronidation.
In this process the heme is broken down into an orangey-yellow pigment known as ‘free’ bilirubin. This is a fat-soluble form of bilirubin that is transported to your liver. Here, bilirubin is metabolised by a liver enzyme called urodine diphosphate glucuronosyltransferase (more easily called UGT) and modified to a water-soluble form. This is known as ‘conjugated’ bilirubin.
This watery version is more easily secreted into bile, a fluid produced by your liver to aid digestion. It travels in the bile through your gall bladder and into your small intestine, where it is converted by bacteria into a variety of pigment substances, primarily urobilinogen. It is eventually excreted from the body in your faeces and urine.
This is how the removal of bilirubin is supposed to work. If you have GS, however, you do not have enough of the UGT enzyme to modify the bilirubin at the normal rate.
This is what causes levels of unmetabolised or ‘unconjugated’ bilirubin to build up in your blood. When testing for bilirubin, a special dye (called a reagent) is added to the blood specimen. Water-soluble conjugated bilirubin will react directly to the addition ofdyes by changing colour. Unconjugated bilirubin, which does not dissolve in water, does not react to the dye until alcohol is added to the solution.
For this reason, unconjugated bilirubin is known as ‘indirect’ bilirubin and its conjugated form as ‘direct’ bilirubin. Added together, they are known as your total serum bilirubin.