Elevated Liver Enzyme Test
ALT, AST and ALP
|There are three major enzymes found in liver cells for which medical testing is frequently performed.
These include Alanine Transaminase (ALT), Aspartate Transaminase (AST)
Alkaline phosphatase (ALP). Liver enzymes are normally located
within the cells and are only released into the bloodstream when the
cell is destroyed. For this reason, there are normally very low
levels of these liver enzymes in the bloodstream and a test result that
indicates elevated amounts of the enzymes indicate increased levels of
liver cell death. AST is also found in cardiac muscle so is
frequently tested to see if heart tissue destruction has occurred.
In that instance, test results would indicate a raised AST level, but
ALT would remain within normal ranges.
different conditions could cause liver enzymes to be elevated.
They are broken down into two major categories, chronic and acute.
Acute occurrences of elevated liver enzymes are not uncommon and can
occur because of infections or even just taking certain medications can
cause short-term increased liver cell death. Chronic elevated
liver enzyme test results indicate a much more severe underlying
problem. Normal liver enzyme for ALT, AST and ALP are listed below.
ALT 9-52 IU/L
AST 10-35 IU/L
ALP 30-120 IU/L
enzyme has particular uses that allow a doctor to help determine the
underlying cause. For instance, as mentioned, AST is also found
within cardiac muscle as well as red blood cells. The cells that
contain ALP reside around the duct system within the liver, so elevated
levels of ALP without corresponding AST and ALT levels pinpoint the
issue to the duct system.
Cirrhosis is long term damage to the liver that results in
scarring. Liver cells are similar to normal body cells where cell
death and cell reproduction are constantly occurring. In the case
of cirrhosis however, the damage to the tissue is so severe that the
body no longer attempts to repair the tissue, but instead produces scar
tissue to isolate the damage. The most common cause of Cirrhosis
is alcoholism. As the scar tissue develops, cell death within the
specific region escalates resulting in long term elevated liver enzyme
Some medications can also lead to a temporary increase in liver enzyme
levels. Statins are a class of medications used to treat high
cholesterol that can cause elevated ALT, AST and ALP levels. If
these medications are anticipated to be used for a long period of time,
the doctor will frequently order periodic liver enzyme tests to ensure
the damage to the liver is minimal. Acetaminophen (commonly known
as Tylenol) can also lead to short term high enzyme levels.
Overdosing or abuse of Acetaminophen can cause permanent liver damage
resulting in scarring and chronic elevated enzyme levels.
As mentioned previously, the cells that contain ALP are found around the
ducts of the liver. One of the most common causes of high ALP
enzyme levels is gallstones or other diseases the block the ducts.
It is also possible for a growth, like a cyst or tumor to impede the
ducts and cause excessive death to the tissue surrounding them.
Finally, obesity must be mentioned. There are direct links to
obesity and chronic liver problems that is usually associated with poor
food choices by individuals. The liver is responsible for removing
many toxins from the body, which is why poor food choices causes stress
on the liver and subsequently could lead to excessive cell death and
elevated liver enzymes.
Reviewed: Peter Sedesse, MD