Jaundice is not a disease but rather a sign that can occur in many different diseases. Jaundice is the yellowish staining of the skin and sclerae (the whites of the eyes) that is caused by high levels in blood of the chemical bilirubin. The color of the skin and sclerae vary depending on the level of bilirubin.
When the bilirubin level is mildly elevated, they are yellowish. When the bilirubin level is high, they tend to be brown.
Bilirubin comes from red blood cells.
When red blood cells get old, they are destroyed. Hemoglobin, the iron-containing chemical in red blood cells that carries oxygen, is released from the destroyed red blood cells after the iron it contains is removed. The chemical that remains in the blood after the iron is removed becomes bilirubin.
The liver has many functions. One of the liver's functions is to produce and secrete bile into the intestines to help digest dietary fat. Another is to remove toxic chemicals or waste products from the blood, and bilirubin is a waste product. The liver removes bilirubin from the blood.
After the bilirubin has entered the liver cells, the cells conjugate (attaching other chemicals, primarily glucuronic acid) to the bilirubin, and then secrete the bilirubin/glucuronic acid complex into bile. The complex that is secreted in bile is called conjugated bilirubin.
The conjugated bilirubin is eliminated in the feces. (Bilirubin is what gives feces its brown color.) Conjugated bilirubin is distinguished from the bilirubin that is released from the red blood cells and not yet removed from the blood, which is termed unconjugated bilirubin.