Bilirubin and Biliverdin - Meaning, Difference Between Them

Bilirubin is a yellowish-coloured pigment and a metabolite of heme. It is formed due to the breakdown of the red blood cells. 

Once the lifecycle of the red blood cells is complete, the haemoglobin present in them undergoes degradation, where the biliverdin formed undergoes further reduction to give bilirubin as an end product.

Accumulation of the bilirubin in the body tissues can be a warning sign of a liver condition. High or increased bilirubin levels in the body can cause serious conditions like hyperbilirubinemia and jaundice. 

There are two types of bilirubin which include:

1. Unconjugated bilirubin (Indirect Bilirubin) :  This type of bilirubin is formed when the red blood cells break down, which travels in the blood and into the liver. Unconjugated or indirect bilirubin is insoluble in water and is extremely toxic to the body. A spike in unconjugated bilirubin can cause unconjugated hyperbilirubinemia.
2. Conjugated bilirubin (Direct Bilirubin) : When unconjugated bilirubin is conjugated by the addition of glucuronic acid, conjugated or direct bilirubin is formed. Conjugated or direct bilirubin is easily soluble in water and is non-toxic to the body. Increased conjugated or direct bilirubin levels in the body lead to conjugated hyperbilirubinemia.

A spike in bilirubin may be due to various liver problems or other medical conditions. Depending on the symptoms, the doctor will examine and diagnose the cause leading to a high bilirubin level.

Biliverdin is a green-coloured pigment found in the bile. During the breaking down of heme, biliverdin is formed as a byproduct. This biliverdin undergoes further breakdown through biliverdin reductase to form bilirubin. Bilirubin, upon oxidation, changes back to biliverdin. 

A high level of biliverdin is usually caused due to improper conversion of biliverdin to bilirubin. Biliverdin spike may also be due to genetic mutation of the biliverdin reductase A-gene.

Bilirubin and biliverdin are derived from the breaking down of the haemoglobin (heme degradation) present in senescent red blood cells. The heme in the senescent red blood cells undergoes degradation by heme oxygenase, leading to the formation of biliverdin, carbon monoxide, and iron. The biliverdin so formed undergoes further reaction where it is converted to bilirubin (unconjugated) by biliverdin reductase.

Parameter	Bilirubin	Biliverdin
Colour	Yellowish	Green
Formation reaction catalysed by	Biliverdin reductase	Heme oxygenase
Symptoms are seen in the case of its rise	Darkened urine The pale colour of the stools  Nausea Vomiting Weight loss Fever Appetite loss.	Green-coloured skin, urine, and other body fluids (green jaundice).
Causes	Jaundice Gallstones Hemolytic anaemia Liver diseases like Hepatitis, Cirrhosis Misfunctioning of the liver Gilbert’s syndrome Problems in the bile duct Drug reaction Blood transfusion reaction	Genetic mutation of the biliverdin reductase A-gene
Test for diagnosis	Physical examination Bilirubin test	Colour changes Lab tests
Disease caused due to its increase	Hyperbilirubinemia Jaundice Kernicterus	Hyperbiliverdinemia (green jaundice)

Bilirubin and biliverdin are formed due to heme breakdown and are essential for the body. Where bilirubin is the end product of heme breakdown, biliverdin is a byproduct. Both bilirubin and biliverdin are found in the bile, which is responsible for digestion.

Jaundice is the most common condition caused due to high levels of biliverdin and bilirubin; hence, reducing the risk of its increase is essential. 

Now that you must be clear about the diseases caused due to the derangement in the levels of bilirubin and biliverdin reach out to HexaHealth in case you notice any such symptoms that point towards a liver or other disorders. HexaHealth has a team of experienced professionals who will help manage your condition without hassle. So get in touch with us right now!