Stercobilin

stercobilin

Stercobilin is a bile pigment that is primarily responsible for the brown color of human feces. It is a tetrapyrrolic bile pigment and a breakdown product of heme from hemoglobin. Stercobilin is formed in the intestines by the bacterial reduction of bilirubin, which is excreted in bile from the liver.

Formation and Metabolism

Stercobilin is produced through a series of metabolic processes. Initially, heme from hemoglobin is broken down into biliverdin and then reduced to bilirubin. Bilirubin is transported to the liver, where it is conjugated with glucuronic acid to form bilirubin diglucuronide. This conjugated bilirubin is excreted into the bile and passes into the intestines.

In the intestines, bilirubin is converted by bacterial action into urobilinogen. Some of the urobilinogen is reabsorbed and excreted in urine as urobilin, while the remainder is further oxidized to form stercobilin, which is excreted in feces.

Clinical Significance

The presence and concentration of stercobilin in feces can be an important diagnostic marker. A lack of stercobilin can result in pale or clay-colored stools, which may indicate a blockage in the bile ducts or liver disease. Conversely, an excess of stercobilin can result in darker stools.

Related Compounds

Stercobilin is closely related to other bile pigments such as urobilin, biliverdin, and bilirubin. These compounds are all involved in the breakdown and excretion of heme.

See Also

• Bilirubin
• Biliverdin
• Urobilin
• Heme
• Hemoglobin
• Liver
• Bile