The body's largest organ, the liver has many responsibilities including converting what you ingest into nutrients and energy, ridding the blood of alcohol and poisons and producing bile, which is needed in digestion. The liver has the ability to regenerate, making new cells and repairing damaged ones, but with more than 100 possible liver diseases, the rate of repair and regeneration cannot always keep up with the rate of damage. When the liver is compromised, there are a number of liver function tests that can be used as indicators of the extent of the damage.
Liver Function Tests
Liver function tests, or LTFs, are administered if you have evidence of liver damage such as jaundice or if your risk of liver disease is higher than normal, or they may be ordered as part of a routine medical examination. A blood test is used to check levels of enzymes such as alanine aminotransferase, or ALT, aspartate transferase, or AST, alkaline phosphatase, or ALP, as well as bilirubin and albumin, among other things.
Alkaline Phosphatase
Alkaline phospatase, ALP, is present in the liver, and if the liver is injured, ALP will leak into the blood stream, causing the level of ALP in the blood to become elevated. ALP is also present in bone, placenta, intestine and kidneys, but the liver and bone have the highest concentration. Each tissue type produces a different type of ALP, called isoenzymes.
Elevated ALP: What it Means
The most common cause of elevated ALP is liver disease or disorders of the bone. In the liver, ALP is normally found on bile duct cells, so if there is an obstruction to the bile ducts, there will be a large increase in the blood level of ALP. Other liver diseases such as cancer, cirrhosis and hepatitis will also cause an increase in ALP levels but to a lesser degree.
Bone Disorder or Liver Disease?
To determine whether the blood ALP level is elevated due to a bone disorder or a liver disease, other test results have to be consulted. If AST, ALT and bilirubin levels are also high, then the ALP is likely to have originated in the liver, while if calcium and phosphorous levels are outside of normal ranges, then it is more likely due to a bone problem. If routine tests fail to distinguish between the possible sources of ALT, then an isoenzyme test can be done to ascertain what body tissue produced the ALP.
Considerations
The American Liver Foundation ranks liver disease among the top 10 causes of death in the US. Some liver diseases can be prevented, and you can make lifestyle choices that promote liver health. A healthy diet, not smoking, limiting alcohol consumption, being careful with medications and avoiding toxins such as those found in insecticides, cleaning agents and chemicals are all ways recommended by the American Liver Foundation for keeping your liver healthy.
