The liver is a remarkable organ responsible for hundreds of vital functions, including filtering toxins from the blood, producing bile for digestion, and synthesizing essential proteins. Liver Function Tests (LFTs), often included in a Comprehensive Metabolic Panel, are a group of blood tests designed to evaluate how well your liver is performing these tasks.
The most common liver enzymes measured are Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). These enzymes are normally contained within liver cells. However, when the liver is injured or inflamed—due to conditions such as viral hepatitis, excessive alcohol consumption, or fatty liver disease—these cells can leak ALT and AST into the bloodstream, resulting in elevated levels on your lab report. ALT is generally considered more specific to the liver, while AST can also be found in the heart and skeletal muscles. Mild elevations are common and may not always indicate serious disease, but they warrant further investigation by your doctor.
Another crucial marker in liver function testing is bilirubin. Bilirubin is a yellowish pigment produced during the normal breakdown of red blood cells. The liver processes bilirubin so it can be excreted from the body in stool. If the liver is not functioning properly, or if the bile ducts are blocked, bilirubin can build up in the blood, leading to a condition known as jaundice, characterized by a yellowing of the skin and eyes.
LFTs also measure Alkaline Phosphatase (ALP), an enzyme found in the liver and bones. Elevated ALP levels can indicate a blockage in the bile ducts or certain bone disorders. By analyzing the pattern of these various markers, your healthcare provider can pinpoint the specific nature of any liver-related issues.