Liver
Function
What Does the Liver Do?
The liver is the largest organ in the body,
weighing around 3.5 pounds (1.6kg). The liver has a
major role in metabolism, digestion, detoxification and elimination of
various substances from the body. While liver transplants are
done, it is best to take good care of this organ so that such extreme
measures never becomes a necessity. See reference (3) for a longer
discussion of liver function.
Definitions
The following terms may be encountered as
you read about liver diseases. Most have not been used in this
brief writeup.
Conjugated - chemically attached to 'something'.
Hepatitis - inflammation of the liver from any
cause.
Hepatotoxic - toxic to liver cells.
Hepatomegaly - abnormal liver enlargement.
Hepatocytes - liver cells.
Jaundice - the whites of your eyes and even your
skin become yellow due to high levels of bilirubin over time.
Metabolism -
the sum of the processes by which a particular substance is handled (as
by assimilation and incorporation or by detoxification and excretion) in
the living body.
Parenchyma - working tissue of the liver
Steatosis - also called fatty liver. It is a
condition in which fat has accumulated within liver cells, but not
causing any specific symptoms.
Diseases of the Liver3
Liver diseases such as hepatitis A, B or C,
cirrhosis, steatosis and drug-induced hepatitis can occur. Hepatitis A,
B or C can be ruled out by lab tests for that condition. Alcohol
can result in liver damage. In cases of prostate cancer, drug-induced
hepatitis is probably the most common disease or inflamed state.
Drug-induced hepatitis
Drug-induced hepatitis is the inflammation and
hepatocellular damage of the liver caused by a drug or combinations of
drugs or possibly by some 'food' supplements or herbal therapies.
These are considered drug side effects or drug toxicities and do not
occur in all patients.
In the case of prostate cancer, drugs such as
ketoconazole, casodex, flutamide, Lovastatin, NSAIDs and others are often stated to carry a risk of elevated
liver enzymes (via damage to liver cells.) Additionally, estrogens
are an example of a drug that can cause cholestatic liver
disease(intrahepatic).
What tests are run to assess liver
function?2
You cannot live
without adequately functioning kidneys and liver. Therefore, it may be
necessary with certain drugs to run some of the following tests periodically
to determine whether those drugs are harming these vital organs. Liver
and kidney insufficiency are also dangerous associated diseases that can
aggravate the problem of cancer. The following tests are often given monthly
as part of the complete metabolic panel with blood drawn before chemotherapy
or during regular monitoring of your disease.
ALP (Alkaline phosphatase).
The ALP enzyme is found in all body tissue, but the primary amounts are
found in the liver, bone and bile ducts and elevated levels may indicate
bone, liver or bile duct disease. Therefore, ALP alone, if elevated, is indicative,
but not definitive of the actual underlying disease. It is possible to differentiate between the sources of the
ALP with tests such as the Bone Specific Alkaline Phosphatase which gives
the individual bone and liver contributions. A greatly elevated value
in men with prostate cancer may indicate metastatic growth in the bones.
Note that some drugs might also lead to increased ALP levels.
ALP Net: Elevated
levels may indicate liver injury or prostate cancer bone metastases or bile
duct obstruction. Healing of fractures can increase ALP.
AST -
aspartate aminotransferase (formerly
called SGOT - serum glutamic-oxaloacetic transaminase). Is elevated in
the case of of any condition involving necrosis (death) of hepatocytes
(liver cells), myocardial cells (heart muscle), or skeletal muscle cells.
Damage from alcohol, a number of diseases, as well as, strenuous exercises
can cause elevated AST. Elevated levels may also be due to a prescription
drug or 'natural' health product you are taking.
AST Net: Elevated
levels may be due to liver, heart, muscles or brain injury.
ALT -
alanine
aminotransferase
(formerly called SGPT - serum glutamic-pyruvic transaminase). Increased in cases of
liver cell damage. ALT is found mainly in the liver, but smaller amounts are
also in the kidneys, heart and muscles. Liver damage from
alcohol, various diseases, strenuous exercise and various prescription drugs
or 'natural' health products can lead to high test values.
ALT Net: Elevated
levels may indicate liver cell injury.
Bilirubin. Other
names include: Total bilirubin; Unconjugated bilirubin; Indirect bilirubin;
Conjugated bilirubin; Direct bilirubin. Total serum bilirubin equals the sum
of direct(conjugated)- and indirect(unconjugated)- bilirubin. Bilirubin is a breakdown product of
hemoglobin(note: red blood cells contain hemoglobin). Total bilirubin
and direct bilirubin are usually measured for screening and/or monitoring
liver or gall bladder problems.
Increased
direct(conjugated) bilirubin may indicate bile duct obstruction, cirrhosis
or hepatitis.
Bilirubin is elevated
in the case of liver disease or with the use of drugs that are toxic to the
liver (hepatotoxic).
Bilirubin Net: May
indicate liver damage, excess breakdown of red blood cells, obstruction to
bile flow. Bilirubin is a component of the digestive juice (bile) produced
by the liver.
TP - Total protein.
Total protein is a rough measure of the total protein in the blood.
Measurements of protein may reflect liver disease, nutritional state, kidney
disease and others. In general, protein consists of albumin and
globulin. Albumin is formed in the
liver; it transports blood constituents. Globulin is a building block
of antibodies, proteins, and clotting factors. Globulin is made up of
about 60 different important proteins.
A decreased value of total protein may indicate liver or kidney disease.
Albumin.
A component of total protein
and is the most abundant protein in blood plasma. It keeps fluid
inside your blood vessels. If levels of albumin are low, there is the
possibility of primary liver disease, kidney disease, tissue damage or
inflammation, and malnutrition (note: this is probably not a complete
list).
Albumin Net: May
indicate liver damage.
Other Lab Tests that may be
Included in a Liver Panel
LDH (lactate dehydrogenase)
is an enzyme found in the kidneys, liver, heart, muscle, brain, lungs
and red blood cells. An increased level may be indicative of disease in one of
those areas. When matched with elevated liver or kidney enzymes, an
elevated LDH confirms disease in one of those organs.
GGT - gamma-glutamyl
transferase. Sometimes used to screen for liver disease and alcohol
abuse. It can also be used to differentiate between liver and bone disease
as a cause of elevated ALP (however, bone specific ALP will also help make
this distinction). A normal GGT combined with a high ALP would
indicate the high ALP is due to bone disease.
Prothrombin
time. Liver disease may lead to prolonged PT values.
Help! My Liver Enzymes are
Elevated. What do I do Now?
This is something you need to talk with
your physician about. Gastroenterologists also are specialists dealing
with the liver and other related organs. In brief, if you can, stop
any drugs that are known to have the potential to damage the liver (e.g.,
ketoconazole). There can also be interactions between drugs that might lead
to elevated liver enzymes -- so you might have to stop several drugs.
Also 'natural' food products/supplements/herbal preparations might cause
liver problems.
It would also be wise to eliminate any
possibility of your having hepatitis A, B or C. There are standard lab
tests for this.
The liver, if not too damaged, will in
time most likely repair itself if the drug causing the damage is stopped.
The use of an extract of milk thistle may help speed up the process.
Silibinin and silymarin are two of these extracts.3
Example Complete Metabolic Panel
Note: the yellow area highlights liver function tests. Reference ranges
may vary from laboratory to
laboratory. HI and LO are relative to the Reference Range.
|
Typical Complete Metabolic
Panel - Blood Tests |
|
Test |
Flag, LO=Low, HI= High |
Result |
Units |
Reference Range4 |
| Sodium |
LO |
136. |
mmol/L |
137 - 145 |
| Potassium |
|
4.0 |
mmol/L |
3.6 - 5.0 |
| Chloride |
|
103. |
mmol/L |
98. - 107. |
| CO2 |
|
30. |
mmol/L |
22. - 31. |
| Alkaline Phosphatase |
|
39. |
U/L |
38. - 126. |
| Total Bilirubin |
|
0.3 |
mg/dL |
.2 - 1.3 |
| AST |
HI |
67. |
U/L |
8. - 50. |
| ALT |
HI |
104. |
U/L |
9. - 72. |
| Albumin |
LO |
3.4 |
g/dL |
3.9 - 5.0 |
| Total Protein |
|
6.8 |
g/dL |
6.3 - 8.2 |
| Creatinine |
|
1.0 |
mg/dL |
0.7 - 1.5 |
| Urea Nitrogen |
|
18. |
mg/dL |
7.0 - 20. |
| Calcium |
|
9.1 |
mg/dL |
8.4 - 10.2 |
| Glucose |
|
92. |
mg/dL |
65. - 110. |
| LDH |
|
516 |
U/L |
313 - 618 |
