Gamma-Glutamyl Transpeptidase (GGT)
What is the GGT?
The full name of GGT is Gamma-glutamyl transpeptidase test; physician also called it Gamma-GT or GGPT. This is a test which helps in determining the level of GGT in the bloodstream. The abnormal high or low level shows alcohol abuse, bone disease & bile duct obstructions are the few names. As a thumb rule, the higher the GGT level the higher would be the chances of liver damage. There may be other situations which might lead to this & hence, other tests will be recommended along with the GGT test.
This test is used to measure the GGT which exists in the blood. As GGT is particularly found in the areas near liver & other organs a raised level of GGT in the blood indicates the flowing of the enzymes out of the liver into the bloodstream & can be identified by its raised level. Many other blood tests are also performed with GGT test to figure out the causes of damaged liver.
C-terminal glutamyl groups splits apart due to this enzyme from amino acids and relocate them to other amino acid or to peptide. It is very important in protection from oxidant injury, amino acid absorption & glutathione metabolism. Even though GGT is presents in many tissues, the main source is liver; therefore GGT is used chiefly as a sensitive indicator of cholestasis. Its life span is around 72 to 96 hours.
This test is being done to determine the GGT level in the blood. GGT enzyme is found in various organs like liver, pancreas, kidney & spleen but the major source of GGT in the blood is the liver.
GGT rises in various diseases that cause bile ducts or severe damage to the liver but is generally unhelpful in making difference between altered causes of liver damage.
The levels of GGT in blood are very delicate to variations in the function of liver. If the liver gets injured the GGT level rises otherwise GGT level present in low level. Among other enzymes GGT is the initial liver enzyme which rises in the blood when any bile ducts which carry bile from the liver to the intestines become obstructed like stones or tumors. So for identifying the bile duct problems this test becomes the most sensitive liver enzyme test. As GGT level get increases with any kind of liver disease hence GGT test is not very important and also helpful in distinguishing b/w various liver diseases.
ALP & GGT both get increased with liver diseases but due to bone disease on ALP gets increased. Hence, GGT will be used as a follow up test to an increased ALP which helps in determining the reason behind high ALP causes due to liver diseases or bone disease.
Consuming a very small amount of alcohol also increases the GGT levels. Heavy drinkers have high GGT levels.
GGT is an enzyme originates in many tissues which include kidneys & liver. Increased GGT indicates that patient is suffering from diseases related to pancreas, liver, biliary system & kidneys. GGT also rose because of consuming alcohol in heavy amount. Usually GGT test recommended as a follow up test to the other tests like bilirubin, SGOT (AST) & ALT. In the basic health screening the measurement of bilirubin & AST is included.
GGT is being used by the physicians to determine the obstacles in the liver disease, pancreatitis & biliary system. It seems that due to many medical conditions such as cancer of liver & pancreas or heavy consumption of alcohol increases the level of GGT in the blood. GGT is also used as an indicator for tumor development and to increase response to treatment.
To better determine the lever function most of the times GGT is used in combination with AST & ALT test. Patient should be suggested to not eat anything for at least 8 to 12 hours prior to the test. In the life extension male & female panels this test is included. The patient’s should take all the medicines prescribed to them. But on the day of sample blood drawn for test patients are suggested not to take their supplements in morning.
GGT is found chiefly in the microsomes & in membrane as totals. In cytoplasm the small portion of GGT i.e. less than 5% is also found. Increased synthesis & disaggregation cause increased activity in serum in the end. It is seen that certain organs in the body respond differently with the GGT levels which can be summarized as under:
- It is seen that GGT levels dose not rise in tissues of pancreas or gastrointestinal tract in the serum surrounding these organs as it is shed not in the serum but in the lumen of both the organs.
- It is seen that GGT is flown through urine & not directly in the bloodstream in kidney region.
- In the region surrounding mammary glands it is seen to release along with milk.
- In the region surrounding reproductive tract such as epididymis it is secreted in the semen.
- Biliary tract is seen to be a main source of serum activity.
GGT test is done to measure the enzyme levels in the blood. In many body tissues GGT gets produced but mainly in gallbladder & liver.
Liver perform many functions in the body like storing the fuel from food and in making protein, also liver helps in removing the toxins & poisons and generates the digestive liquid which helps the body in absorbing the fat. Gallbladder works as storage of bile until it is needed.
GGT is a kind of liver enzyme which involves in the transportation of peptides & amino acids into cells and also into glutathione metabolism. GGT majorly found in the cells of liver & gets affected very quickly with the consumption of alcohol. Increased level of GGT is found in bile duct obstructions, alcoholism obesity, drug abuse, cholangitis & liver disease & decreased level of GGT is found in very low level of magnesium, hypothyroidism & hypothalamic malfunction.
GGT is an enzyme that absorbs glutathione presents outside the cells and can be persuaded by many ethanol, xenobiotic & drugs. The other test performed for liver is called ALT.
Normal GGT levels for man & woman is as follows:
- The normal GGT level for adult woman range b/w: 0 To 45 Universal/Local (U/L)
- The normal GGT level for man range b/w: : 0 To 65 Universal/Local (U/L)
Due to fatness GGT level increases.
For many tissues GGT exists in their cell membranes which include seminal vesicles, heart, gallbladder, bile duct, brain, spleen, pancreas & kidneys. While transferring the amino acids across the leukotriene metabolism & cellular membrane the GGT is also involved in it. GGT also has its involvement in glutathione metabolism by transferring the glutamyl moiety to various acceptor molecules which includes H2O, peptides & certain L-amino acids, leaving the cysteine product to reserve intracellular homeostasis of oxidative stress. Is the general reaction for this is:
(5-L-glutamyl)-peptide + an amino acid peptide + 5-L-glutamyl amino acid
Reason why it is ordered:
The reason behind the GGT test is to provide info about diseases cause due to hepatobiliary, to get the info about how liver is functioning & to figure out the alcohol ingestion. The other reason to perform GGT test is to differentiate the hepatic disease & skeletal disease when serum alkaline phosphatase is increased.
When patient go to the physician while suffering from jaundice which is a symptom of liver disease than physician will use a GGT test to figure out the issue. Jaundice is the initial symptom of liver disease which is caused due to high bilirubin level in the blood. This material is usually collected in the liver, processed and converted into bile which is a digestive juice. In case of damaged liver this function will not work at all & also stops bilirubin to start accruing in the blood stream. Jaundice can be happen due to food poisoning or by consuming alcohol in large amount.
If the patient is nonalcoholic than his liver can be damaged due to consumption of contaminated food or drink which will results in viral hepatitis. Viral hepatitis is an issue which takes around one month bed rest & complete change in diet table to get cured. Change in diet table means reducing the amount of fat in diet & also reduce consuming the spicy food. If people with higher alcohol consumption have their GGT level increases than it’s a time for them to reduce the alcohol consumption to nil because further elevation in GGT can cause cirrhosis of the liver.
Those who have increased ALP level for them GGT test will be ordered. Even there is no symptom for liver disease present, ALP test is ordered or as a part of a routine liver panel for screening. If the ALP test result is high but the test result of other tests such as ALT & AST is not increased than GGT test will be ordered just to figure out that increased level of ALP is caused due to liver disease or due to bone disease. A physician usually asks to have GGT test as well with other tests to evaluate a patient who have symptoms and signs that suggest liver disease. Some examples of symptoms of liver injury are:
- Abdominal Swelling
- Sever Itching
- Abdominal Pain
Elevated GGT in many diseases cause damage to bile ducts & liver, but it generally not help in differentiate between various reasons of liver damage. GGT also helps to determine the reason of an elevated ALP. Patients who are consuming alcohol from past many years, GGT will be performed to check that they are properly performing the treatment program or not.
GGT test will be asked by the physician along with the other tests as a follow up if any patient have a symptom or sign that indicates a liver disease.
How the GGT test is performed?
GGT test is useful in determining the reason behind the increased ALP. GGT & ALP level get increased due to liver or bile duct diseases but only ALP level get increased due to bone disease IF GGT level is normal & ALP level is high in any patient than this can be caused most likely due to bone disease.
GGT test is performed to identify the bile duct obstruction or liver disease. It is generally performed in combination or as follow of other liver tests like bilirubin, AST, ALT & ALP. Elevated GGT level shows that the liver is infected but cannot tell the reason behind of infection. There are many reasons cause elevation in GGT level such as congestive heart failure, consumption of alcohol or any liver disease.
What will be the preparation needed before the test?
Pretest preparation is not required. But there are few medicines which can affect the test result hence, patient should inform the physician if he/she is going under any medications, so the physician can suggest accordingly.
Wear a short sleeves shirt on the test day so it will be easier for the physician to take the blood sample.
Normal Values and Test Result:
The physician is not concerned about the high or low level of GGT, but he can tell that there are doubts that patient have any liver disease.
Elevated GGT indicates that there is any liver disease is present but cannot detect the exact disease. The higher the GGT level is the higher will be the chances of liver to get damaged. Few causes of elevated GGT is as follows:
- Liver Disease
- Alcohol consumption
- Congestive heart failure
- Usage of prescribed and non-prescribed drugs like NSAIDs, Lipid lowering drugs, Histamine blockers, anticonvulsants, antifungal agents or antidepressants
- Hormones like testosterone
.GGT level get decreases by consuming clofibrate and birth control pills.
- For females less than 45 years of age the normal GGT level is 5 – 27 Universal/Local (U/L).
- For females above 45 years & in males the normal GGT level is 6 – 37 Universal/Local (U/L).
As GGT levels fluctuates may times in a day hence, the increase GGT level doesn’t mean anything but the existence of jaundice is much enough to confirm that some type of liver damage is present. After this GGT and ALP test comparison will be done.
ATP and ALT test are the other enzyme tests. Due to liver inflammation there are other enzymes which start to leak out of the liver.
Some of the possible combination of high liver enzymes & what does it means is as follows:
If GGT is above 100, and ALT is less than 80 and ALP is less than 200
This could mean that:
- Patient is consuming alcohol in high amount.
- Patient is consuming drugs like heroine or ICE which is also known as recreational drugs.
- Patient is diabetic.
- The liver of patient is fatty.
- The triglycerides level is very high in patient.
- Patient is consuming such drugs which stimulate the liver to produce more enzymes.
Note: For some patients the 120 GGT level is also normal, without having any liver disease.
If GGT is above 100, and ALT is less than 80 and ALP is above 200
This could mean that:
- Due to gall stone in bile ducts it will slow down or obstructs the flow of bile, very swollen bile ducts or a tumor outside or inside the liver which is pressing on the bile ducts.
- The flow of bile ducts slows down due to excess consumption of alcohol or drugs.
- Cirrhosis can alter the bile ducts and cause reduction in the flow of bile.
- The ALP can be raised due to bone disease.
Note: When the flow of bile reduced or obstructed, the bilirubin level gets increased to above 20 which will cause jaundice.
If GGT is above 100, ALT is above 80 and ALP is less than 200
This could mean that:
- If the liver cells get infected by some viruses like Epstein Barr Virus or Hepatitis A, B or C viruses. Patient is consuming drugs and alcohol in excess.
- Liver of the patient is fatty.
If GGT is 100, ALT is above 80 and ALP is above 200
This means that the cells of liver are damaged and the flow of bile is reduced or obstructed which can cause following liver diseases:
- Due to alcohol or drug toxicity or viral infections can cause severe hepatitis.
- Hepatitis for long time can be caused due to alcohol excess or autoimmune disease or because of viral infection.
- Flow of bile gets obstructed due to tumor inside or nearby area of liver.
- Cause cirrhosis.
Causes of increased GGT:
Elevated GGT indicates that there is any liver disease is present but cannot detect the exact disease. The higher the GGT level is the higher will be the chances of liver to get damaged. GGT level increased due to liver disease but it also raised due to other conditions like alcohol consumption and congestive heart failure. Increased GGT level helps in identifying the cause of elevated ALP due to bone disease.
Low or normal GGT levels shows that elevated ALP is caused due to bone disorder and also it indicates that the patient don’t have any liver disease.
Alcohol consumption in very less amount in a day an also slightly increases the GGT level. Physician can ask for the retest if alcohol consumption is the reason of increased GGT.
During heart failure the GGT level can get elevated. Some studies have shown that people with increased GGT levels have an elevated risk of dying from heart disease, but the reason for this association is not known.
Increased GGT level can be caused due to some medicines like carbamazepine, barbiturates and phenytoin. It get increased due to several other prescribed and non-prescribed drugs which includes lipid-lowering drugs, NSAIDs, antibiotics, medicines used to cure extra stomach acid production, antidepressants, antifungal agents, and hormones like testosterone. Consumption of birth control pills & clofibrate decreases the GGT level.
GGT level also elevates due to smoking.
AS the age of women increases the GGT level increases but this same will not go with the men and men GGT levels will always be higher than the women GGT level.
- Drug effects
Secondary to the therapeutic drugs which causes cholestasis an increase in GGT is observed. Rise in corticosteroid /anticonvulsant therapy, probably which is secondary to liver injury which results in causing localized cholestasis or biliary hyperplasia. Along with corticosteroids a rise in GGT is also seen due to induction of GGT synthesis 5 days later to corticosteroid administration an increase in GGT occurs.
a) Neonates: Apart from horses Colostrum is found in all the species and generally have higher level of GGT. Higher level of GGT is a sensitive indicator of inert transfer and after suckling within 24 hours the level of GGT goes high. A high level of GGT such as 1000 x adult levels in 2-3 day old puppies may be observed which again goes down over the time period. In calves, higher level of GGT is helpful in checking the effectiveness of flaccid transfer Even, GGT can be higher in neonates though foals do not derive GGT from the colostrum of mares.
b) Breed: As compared to horses, donkeys & burros have 2 to 3 time’s higher GGT level.
3. Disease effects
An increase in GGT is majorly due to the abnormal increase in the number of normal cells in normal arrangement in an organ or tissue which is secondary to induction of synthesis.
a) Hepatobiliary disease: This is generally pertaining to or emanating from the liver, bile ducts and gallbladder and in small animals, like cat GGT is a sensitive indicator of biliary hyperplasia and cholestasis wherein GGT increases may precede increases in ALP. This rise is a major indicator of liver disease in this species. Small animal if treated with CCl4 toxicity will not higher level of GGT.
In large animals, GGT is a sensitive test for gall bladder is a good marker for pyrrolizidine alkaloid toxicity in ruminants and cholestasis. In larger animals such as horses, higher fold increases in GGT compared to AST and ALP are seen in cholangiohepatitis In order to evaluate response to antibiotic therapy in this disorder, monitoring of GGT levels is useful in such species. GGT has been shown to increase with hepatocellular necrosis due to CCL4 toxicity. However, it is not clear if this is truly due to necrosis (of biliary epithelium or hepatocytes) or is secondary to cholestasis/biliary hyperplasia induced by the necrosis. GGT is considered a better marker of biliary tract disorders in large animals than ALP.
b) Renal disease: GGT is uttered on the membranes of proximal renal tubular epithelial cells. Due to the cell injury GGT sheds into the urine and not in blood An increase in GGT levels can be due to Dilantin, an anti-seizure medication, and phenobarbitol, an antiseizure medication and sedative, and decreased by clofibrate, an anticholesterol drug, and birth control pills. High GGT levels are related with liver diseases such as liver tumors, hepatitis, cirrhosis, and jaundice, myocardial infarction, pancreatic cancer and pancreatitis and viral infections such as Epstein-Barr, cytomegalovirus (CMV) and Reye's syndrome.
Fatty Liver and elevated GGT
Fatty liver is caused due to overweight, high consumption of alcohol & obesity related with metabolic syndrome and insulin resistance. Both alcoholic and nonalcoholic fatty liver can leads towards the major liver disease such as liver cancer, cirrhosis & inflammation. Treating the liver disease at initial stage as compare to treatment of advanced liver disease is the best approach to deal with such conditions. Serum GGT is one of the best indicators for heavy alcohol consumption, which has a comparatively high specificity and sensitivity. As the measurement of this enzyme is easy and cheaper hence, it is being used to detect the heavy alcohol consumption level at initial stage only. BMI and sex is also the cause of influenced serum GGT activity along with the amount of alcohol consumption.
What is a High GGT Level?
It is a liver enzyme. It is also called with the name GGTP or g-GTP. This test determines the level of GGT and used to detect liver damages. The diseases which cause liver and pancreas damage increase the GGT level.
GGT is limited inside the cells of the liver and damaged to these cells leaks enzyme in the bloodstream which can be detected with a blood test only. Enzyme is also contained in pancreatic cells.
GGT level more than 27 units per liter is considered high for the women under 45 years of age & 38 units per liter is considered high for the women more than 45 years and for all aged groups men. The normal level for adults is also the normal levels for children’s. For new born babies the normal value is five times higher than normal values for adult. The normal values differ from lab to lab.
While going through the GGT/other enzymes test, as in these test blood is drawn and the patient is not allowed to eat anything usually before 8 hours. Physician should be informed if patient is taking any medicine or supplements before he takes the sample. Due to sensitivity GGT can be raised without any symptoms. This increment is not for a long time and can be caused to consumption of alcohol before 24 hour of the test or due to some medication. GGT test will be re-performed if other liver enzymes don’t have any issues. If either GGT level or other liver enzyme is raised than further testing will be required to identify the cause.
As the consumption of alcohol almost comes to nil the GGT level will also decreases to normal. After stop consuming the alcohol it takes around one month for GGT to come back to normal. Not consuming alcohol will reduce the chances of any more damage to liver and it will also improve the functions of liver.
Significance of High GGT Levels
Elevated GGT levels are related with liver diseases like:
- Viral Infections
- Pancreatic Cancer
- Myocardinal Infection
- Heavy alcohol consumption
- Liver tumors.
Among all the tests performed for liver enzymes, GGT is just a part of those tests. Each test has different results about the condition of liver. To reach a diagnosis the results of all tests will be interpreted.
Most of the time ALP test is suggested along with GGT test. Some times this test is ordered after seeing the GGT test or may be ordered before the GGT test or in collaboration. The ALP test is ordered to distinguish between the liver and bone disease. Decrease ALP level shows less chances of liver disease. For checking the liver disease or disorder other test can also be ordered like ALT, AST, bilirubin & liver panel test.
Abnormal values of both or any one of these test doesn’t assures the presence of liver disease. There are several things which have an impact on the results of the test for e.g. gender, medications & alcohol consumption. Not only the prescribed drugs affect the test result; some other drugs like birth control pills also affect the test results.