Bile acids are a large family of steroids, which has a carboxyl group in the side chain. They are predominantly found in the bile of mammals and other vertebrates. In the liver, bile acids can conjugate with taurine or glycine and form bile salts. Chenodeoxycholic acid and cholic acid are the most abundant bile acids in human bile and they are the primary bile acids synthesized in the liver. Deoxycholic and lithocholic acids are the major secondary bile acids and they are formed by the action of intestinal bacterial bacteria on primary bile acids.