Bile Acids

Bile acids are synthesised in the liver as a breakdown product of cholesterol and are secreted into the gall bladder. The primary bile acids synthesized in the human liver are cholic acid and chenodeoxycholic acid. They are released into the small intestine where they solubilise dietary lipids such as cholesterol aiding their absorption. Bile acids are reabsorbed from the portal blood by hepatocyte extraction and re-excreted into bile, passing through the enterohepatic circulation several times before final excretion. As liver function decreases the efficiency of extraction of bile acids from the blood declines, concentrations within blood therefore increase. Bile acid levels also rise when bile flow is reduced or blocked (cholestasis) and additional bile acids escape into the bloodstream.

The measurement of total bile acids is required for the identification of intrahepatic cholestasis of pregnancy and in patients with progressive familial intrahepatic cholestasis (PFIC) where plasma total bile acid concentrations are increased.