step in detecting liver damage is a simple blood test
to determine the presence of certain liver enzymes in
the blood. Under normal circumstances, these enzymes
reside within the cells of the liver. But when the
liver is injured, these enzymes are spilled into the
most sensitive and widely used of these liver enzymes
are the aminotransferases. They include aspartate
aminotransferase (AST or SGOT) and alanine
aminotransferase (ALT or SGPT). These enzymes are
normally contained within liver cells. If the liver is
injured, the liver cells spill the enzymes into blood,
raising the enzyme levels in the blood and signaling
the liver damage.
are the aminotransferases?
aminotransferases catalyze chemical reactions in the
cells in which an amino group is transferred from a
donor molecule to a recipient molecule. Hence, the
terms can sometimes be confusing, as is the case with
these enzymes. Another name for aminotransferase is
transaminase. The enzyme aspartate aminotransferase
(AST) is also known as serum glutamic oxaloacetic
transaminase (SGOT); and alanine aminotransferase
(ALT) is also known as serum glutamic pyruvic
transaminase (SGPT). To put matters briefly, AST =
SGOT and ALT = SGPT.
where are the aminotransferases?
is normally found in a diversity of tissues including
liver, heart, muscle, kidney, and brain. It is
released into serum when any one of these tissues is
damaged. For example, its level in serum rises with
heart attacks and with muscle disorders. It is
therefore not a highly specific indicator of liver
is, by contrast, normally found largely in the liver.
This is not to say that it is exclusively located in
liver but that is where it is most concentrated. It is
released into the bloodstream as the result of liver
injury. It therefore serves as a fairly specific
indicator of liver status.
are normal levels of AST and ALT?
range of values for AST (SGOT) is from 5 to 40 units
per liter of serum (the liquid part of the blood).
range of values for ALT (SGPT) is from 7 to 56 units
per liter of serum.
elevated AST and ALT mean?
and ALT (SGPT) are sensitive indicators of liver
damage from different types of disease. But it must be
emphasized that higher-than-normal levels of these
liver enzymes should not be automatically equated with
liver disease. They may mean liver problems or they
may not. The interpretation of elevated AST and ALT
levels depends upon the whole clinical picture and so
it is best done by doctors experienced in evaluating
precise levels of these enzymes do not correlate well
with the extent of liver damage or the prognosis
(outlook). Thus, the exact levels of AST (SGOT) and
ALT (SGPT) cannot be used to determine the degree of
liver disease or predict the future. For example,
patients with acute viral hepatitis A may develop very
high AST and ALT levels (sometimes in the thousands of
units/liter range). But most patients with acute viral
hepatitis A recover fully without residual liver
disease. For a contrasting example, patients with
chronic hepatitis C infection typically have only a
little elevation in their AST and ALT levels. Some of
these patients may have quietly developed chronic
liver disease such as chronic hepatitis and cirrhosis
(advanced scarring of the liver).
liver diseases cause abnormal aminotransferase levels?
highest levels of AST and ALT are found with disorders
that cause the death of numerous liver cells
(extensive hepatic necrosis). This occurs in such
conditions as acute viral hepatitis A or B, pronounced
liver damage inflicted by toxins as from an overdose
of acetaminophen (brand-name Tylenol), and prolonged
collapse of the circulatory system (shock) when the
liver is deprived of fresh blood bringing oxygen and
nutrients. AST and ALT serum levels in these
situations can range anywhere from ten times the upper
limits of normal to thousands of units/liter.
moderate elevations of the liver enzymes are
commonplace. They are often unexpectedly encountered
on routine blood screening tests in otherwise healthy
individuals. The AST and ALT levels in such cases are
usually between twice the upper limits of normal and
several hundred units/liter.
common cause of mild to moderate elevations of these
liver enzymes is fatty liver. In the United States,
the most frequent cause of fatty liver is alcohol
abuse. Other causes of fatty liver include diabetes
mellitus and obesity. Chronic hepatitis C is also
becoming an important cause of mild to moderate liver
enzyme elevations. Please visit the Hepatitis C forum
in the Diseases & Treatments section of
MedicineNet for more information.
medications cause abnormal aminotransferase levels?
A host of
medications can cause abnormal liver enzymes levels.
· Pain relief medications such as aspirin, ibuprofen (Advil, Motrin), neproxen
(Narosyn), diclofenac (Voltaren), and phenybutazone (Butazolidine)
· Anti-seizure medications such as phenytoin (Dilantin),
valproic acid, carbamazepine (Tegretol), and
· Antibiotics such as the tetracyclines, sulfonamides,
isoniazid (INH), sulfamethoxazole, trimethoprim,
· Cholesterol lowering drugs such as the “statins” (Mevacor,
Pravachol, Lipitor, etc.) and niacin
· Cardiovascular drugs such as amiodarone (Cardarone),
hydralazine, quinidine, etc.
· Anti-depressant drugs of the tricyclic type
drug-induced liver enzyme abnormalities, the enzymes
usually normalize weeks to months after stopping the
are less common causes of abnormal aminotransferase
common causes of abnormal liver enzymes in the United
States include chronic hepatitis B, hemachromatosis,
Wilson’s disease, alpha-1-antitrypsin deficiency,
and autoimmune hepatitis. Though not as common as
hepatitis C, hepatitis B can cause chronic liver
disease with persistently abnormal liver enzymes.
is a genetic (inherited) disorder in which there is
excessive absorption of dietary iron leading to
accumulation of iron in the liver with resultant
inflammation and scarring of the liver.
disease is an inherited disorder with excessive
accumulation of copper in diverse tissues including
the liver and the brain. Copper in liver can lead to
chronic liver inflammation, while copper in brain can
cause psychiatric and motor disturbances.
deficiency is an inherited disorder in which the lack
of a glycoprotein (carbohydrate-protein complex)
called alpha-1-antitrypsin lead to chronic lung
disease (emphysema) and to liver disease.
hepatitis results from liver injury brought about by
the body’s own antibodies and defense systems
attacking the liver.
abnormal liver enzymes can be a sign of cancer in the
liver. Cancer arising from liver cells is called
hepatocellularcarcinoma or hepatoma. Cancers spreading
to the liver from other organs (such as colon,
pancreas, stomach, etc) are called metastatic
healthy people evaluated for mild to moderate rises in
of healthy patients with abnormal liver enzymes needs
to be individualized. A doctor may ask for blood test
data from old records for comparison. If no old
records are available, the doctor may repeat blood
tests in weeks to months to see whether these
abnormalities persist. The doctor will search for risk
factors for hepatitis B and C including sexual
exposures, history of blood transfusions, injectable
drug use, and occupational exposure to blood products.
A family history of liver disease may raise the
possibility of inherited diseases such as
hemachromatosis, Wilson’s disease, or alpha-1-
pattern of liver enzyme abnormalities can provide
useful clues to the cause of the liver disease. For
example, the majority of patients with alcoholic liver
disease have enzyme levels that are not as high as the
levels reached with acute viral hepatitis and the AST
tends to be above the ALT. Thus, in alcoholic liver
disease, AST is usually under 300 units/liter while
the ALT is usually under 100 units/ liter.
or medication is responsible for the abnormal liver
enzyme levels, stopping alcohol or the medication
(under a doctor’s supervision only) should bring the
enzyme levels to normal or near normal levels in weeks
to months. If obesity is suspected as the cause of
fatty liver, weight reduction of 5% to 10% should also
bring the liver enzyme levels to normal or near normal
abnormal liver enzymes persist despite abstinence from
alcohol, weight reduction and stopping certain
suspected drugs, blood tests can be performed to help
diagnose treatable liver diseases. The blood can be
tested for the presence of hepatitis B and C virus and
their related antibodies. Blood levels of iron, iron
saturation, and ferritin (another measure of the
amount of iron stored in the body) are usually
elevated in patients with hemachromatosis. Blood
levels of a substance called ceruloplasmin are usually
decreased inpatients with Wilson’s disease. Blood
levels of certain antibodies (anti- nuclear antibody
or ANA, anti-smooth muscle antibody, and anti-liver
and kidney microsome antibody) are elevated in
patients with autoimmune hepatitis.
and CAT scan of the abdomen are sometimes used to
exclude tumors in the liver or other conditions such
as gallstones or tumors obstructing the ducts that
drain the liver.
biopsy is a procedure where a needle is inserted
through the skin over the right upper abdomen to
obtain a thin strand of liver tissue to be examined
under a microscope. The procedure is oftentimes
performed after ultrasound study has located the
liver. Not everybody with abnormal liver enzymes needs
a liver biopsy. The doctor will usually recommend this
procedure if 1) the information obtained from the
liver biopsy will likely be helpful in planning
treatment, 2) the doctor needs to know the extent and
severity of liver inflammation/damage, or 3) to
evaluate the effectiveness of treatment.
biopsy is most useful in confirming a diagnosis of a
potentially treatable condition. These potentially
treatable liver diseases include chronic hepatitis B
and C, hemachromatosis, Wilson’s disease, autoimmune
hepatitis, and alpha-1-antitrypsin deficiency.
about monitoring aminotransferase levels?
usually most helpful is serial testing of AST (SGOT)
and ALT (SGPT) over time to determine whether the
levels are going up, staying stable, or going down.
For example, patients undergoing treatment for chronic
hepatitis C should be monitored with serial liver
enzyme tests. Those responding to treatment will
experience lowering of liver enzyme levels to normal
or near normal levels. Those who develop relapse of
hepatitis C after completion of treatment will usually
develop abnormal liver enzyme levels again.
about other liver enzymes?
AST and ALT, there are other enzymes including
alkaline phosphatase, 5’-nucleotidase (“5 prime”
nucleotidase), and gamma-glutamyltranspeptidase (GGT)
that are often tested for liver disease.
We have restricted this
consideration of liver enzymes to AST and ALT because
they are biochemically related to each other and, more
importantly, they are the two most useful liver