Also found in: Dictionary, Thesaurus, Medical, Wikipedia.


The predominant orange pigment of bile. It is the major metabolic breakdown product of heme, the prosthetic group of hemoglobin in red blood cells, and other chromoproteins such as myoglobin, cytochrome, and catalase. The breakdown of hemoglobin from the old red cells takes place at a rapid rate in the reticuloendothelial cells of the liver, spleen, and bone marrow. The steps in this breakdown process include denaturation and removal of the protein globin, oxidation and opening of the tetrapyrrole ring, and the removal of iron to form the green pigment biliverdin, which is then reduced to bilirubin by the addition of hydrogen. The formed bilirubin is transported to the liver, probably bound to albumin, where it is conjugated into water-soluble mono- and diglucuronides and to a lesser extent with sulfate. See Liver

In mammalian bile essentially all of the bilirubin is present as a glucuronide conjugate. Bilirubin glucuronide is passed through the liver cells into the bile caniculi and then into the intestine. The bacterial flora further reduces the bilirubin to colorless urobilinogen. Most of the urobilinogen is either reduced to stercobilinogen or oxidized to urobilin. These two compounds are then converted to stercobilin, which is excreted in the feces and gives the stool its brown color. See Hemoglobin

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



C33H36O6N4, a bile pigment; molecular mass 584.68. Brown crystals. Bilirubin is an intermediate product of the decomposition of hemoglobin that takes place in the macrophages of the spleen, liver, and bone marrow. It is formed by the enzymatic reduction of biliverdin. It is present in small quantities in the plasma of vertebrate animals and man (0.2–1.4 mg percent in a healthy person). When the outflow of bile is made difficult (obstruction of the bile ducts), and in some liver diseases, the bilirubin concentration increases in the blood (causing jaundice), and it appears in the urine. Hence, the presence of bilirubin in blood or urine is a diagnostic test.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


C33H36N4O6 An orange, crystalline pigment occurring in bile; the major metabolic breakdown product of heme.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The underestimation of TcB to TSB levels by >25.5-51 [micro]mol/l in 13.2% of the studied infants led us to recommend that while the infant is under phototherapy a confirmatory TSB measurement should be done when TcB level is <51 [micro]mol/L below the bilirubin level at which phototherapy should be discontinued.
In this study, we aim to evaluate the association between serum bilirubin concentration and the extent of peripheral small nerve dysfunction by using ESC level detected by the SUDOSCAN in Chinese patients with type 2 diabetes.
Total bilirubin levels were monitored every 6 hours throughout the phototherapy.
With the box, BiliScreen was around 90% as accurate as a blood test in identifying concerning levels of bilirubin in a small, 70-person clinical study.
A recent study in the journal Pediatrics showed BiliCam provided accurate estimates of bilirubin levels in 530 infants.
The global prevalence of co-infection is still anonymous and underestimated.6 Altered Prothrombin time (PT), serum albumin, and serum bilirubin are evident of well-being of liver.
We used the Spearman approach to evaluate the correlations between serum bilirubin and demographics or laboratory parameters.
Direct bilirubin (DB) or CB tests (DB/CB) are cheap and widely available.
Exclusion criteria were clinical or laboratory evidence of severe systemic diseases (such as cancer, renal failure, or heart failure), goiter, liver dysfunction (activities of alanine aminotransferase higher than 3-fold the upper limit of the normal range (120 U/L); or total bilirubin level higher than 17.1 [micro]mol/L), or HIV-AIDS.
Bilirubin is commonly measured in lab tests as a marker for liver or blood health, and high levels may indicate disease.
Bilirubin is a by-product of the daily natural breakdown and destruction of red blood cells in the body.
Total serum bilirubin (TSB) measurement is the gold standard test1 to identify those with significant hyperbilirubinaemia (around 10%) from those who don't require intervention (around 90%)4.