Gamma-glutamyl transferase (GGT)

What sample is needed for Gamma-glutamyl Transferase?

1. The venous blood is needed to prepare the serum.
2. The serum is stable for one month at 4 °C.
3. The serum can be stored for one year at -20 °C.
4. Heparinized samples interfere with various methods.

What are the Indications for Gamma-glutamyl transferase (GGT)?

1. This test is performed to assess liver dysfunction.
2. This is also useful for detecting alcohol-induced liver cell injury and chronic alcoholism.
3. This test can detect the slightest degree of cholestasis.
4. GGT is very sensitive to biliary obstruction, cholangitis, and cholecystitis.
5. GGT is a good marker for pancreatic, prostatic, and liver cell carcinomas.
6. GGT level indicates remission and recurrence.

What are the precautions for Gamma-glutamyl transferase (GGT)?

1. Keep in mind that the value may be low in late pregnancy.
2. Drugs that decreased the value are Clofibrate and oral contraceptives.
3. Drugs that increase the value are Alcohol, Dilantin, and Phenobarbital.
4. GGT is raised in patients who are taking antiepileptic drugs.

How will you define Gamma-Glutamyl-transferase (GGT)?

1. γ-glutamyl-transferase is a membrane-bound enzyme in the liver and cells lining the bile ductules and bile canaliculi.
2. γ-glutamyl-transferase, formerly called gamma-glutamyltranspeptidase, is mainly present in hepatocytes.
3. To a lesser extent, it is present in the kidneys, biliary tract epithelium, intestine, pancreas, brain, heart, and spleen.
4. GGT activity is also seen in the capillary endothelium.
5. GGT is responsible for the extracellular metabolism of glutathione, and it is the main antioxidant in the cells.
6. Serum GGT is elevated in the newborn and returns to adult levels by 4 months of age.
7. GGT value may be higher in obese patients than in lean people.

What is the biochemical function of Gamma-glutamyl-transferase (GGT)?

1. γ-Glutamyl Transpeptidase is one of many peptidases that cleave terminal peptide bonds of proteins or peptides.
2. The C-terminal amino acid must be glutamic.
3. Specificity resides in the (γ) Glutamyl portion of the substrate.
4. Three different reactions have been attributed to this enzyme:
   1. Hydrolysis.
   2. Internal transpeptidation.
   3. External transpeptidation.
5. Glutathione is the common substrate of this enzyme in the body.
   1. This enzyme participates in amino acid transport by transferring the γ-Glutamyl portion of glutathione to other amino acids, enabling them to cross cell membranes more easily.
6. GGT is present in the following:
   1. Liver.
   2. The proximal tubule of the kidney.
   3. Brain.
   4. Pancreas.
   5. Intestine.
   6. Prostate.
   7. Capillary endothelial cell.

What is the concentration of the Gamma-glutamyl-transferase (GGT) at different sites?

1. The main concentration is present in the hepatocytes.
2. GGT is found in the biliary tree’s epithelial cells, mostly in the interlobular bile ducts and bile ductules. This is why it is susceptible to biliary injury.
   1. GGT is present in the kidney, pancreas, spleen, heart, intestine, brain, and prostate gland.
   2. GGT level is higher in men because of the additional amount due to the prostate.
   3. The kidney has a maximum amount, but the liver is considered the normal source of serum activity.
   4. It is found throughout the hepatobiliary system and other tissues.
3. GGT is present in cytoplasmic microsomes and at the cell membrane.

4. The Minimal amount detected in the endothelium of capillaries.
5. GGT participates in the transfer of amino acids and peptides across the cell membrane.

What is the importance of the gamma-glutamyl-transferase (GGT)?

1. This test has been useful in detecting male at-risk drinkers (Not in females).
2. This is most applicable to an alcohol screening program.
3. It returns to normal after abstinence from alcohol for 3 weeks.
4. It can be used as a follow-up marker of alcohol intake.
5. It is a more sensitive indicator of liver disease in children than alkaline phosphatase.
6. This is a sensitive test for liver cell injury and its correlation with alkaline phosphatase levels.
7. GGT is raised in acute myocardial infarction, and the mechanism is unclear.
   1. If it occurs in the first 7 days, it may be due to liver cell injury.
   2. Otherwise, it is usually raised in 1 to 2 weeks.
8. However, its raised level is nonspecific because it is raised in cardiac, pulmonary, pancreatic, renal disorders, diabetes, and alcoholism.
9. GGT correlates with alkaline phosphatase in obstructive jaundice and metastatic liver infiltration.
   1. In such a case, GGT is more sensitive and specific.
10. GGT is not elevated in bone disease, whereas GGT and alkaline phosphatase are elevated in liver disease.
11. The overall clinical significance is limited.

What are the functions of the gamma-glutamyl-transferase (GGT)?

1. GGT transports amino acids across the cell membrane.
2. GGT is a sensitive indicator of liver disease, especially hepatobiliary obstruction.
3. GGT is not raised in bone, muscle, and hemolytic anemia.

• GGT is normal with raised alkaline phosphatase, which indicates skeletal muscle disease.
• GGT raised with alkaline phosphatase indicates hepatobiliary disease.

What is the normal value of Gamma- Glutamyl-Transferase (GGT)?

Source 2

• Male and female age 45 years and older = 8 to 38 units/L  (8 to 38 IU/L)
  • Female younger than 45 years = 5  to 27 units/L (5 to 27 IU/L)
  • Older people = Slightly higher than the adults
• Newborn = 5 times higher than adults.
  • Child = Similar to adult level.

Another Source

• Male = 7 to 47 U/L.
• Female = 5 to 25 U/L.
• Newborn = 5 times higher than an adult.
  • Another reference
    • Adult male = up to 55 U/L.
    • Adult female = 38 U/L.
    • The newborn is 6 to 7 times higher than the adults.
      • It is like an adult after 5 to 7 months.

What are the causes of elevated Gamma-Glutamyl-Transferase (GGT)?

1. Obstructive liver disease and posthepatic obstruction.
   1. This may reach 5 to 30 times the normal value.
2. Infectious hepatitis, where the rise is 2 to 5 times the normal value. It is seen in 90% of the cases.
3. Liver diseases such as cirrhosis.
4. The mild increase in the fatty liver.
5. Infectious mononucleosis,
6. Renal transplant.
7. It may be increased in renal failure.
8. Hyperthyroidism.
9. Diabetes mellitus.
10. Pancreatitis.
    1. The increase may be 5 to 15 times the normal value.
11. Myocardial infarction.
    1. There is an increase in 50% of the cases in AMI cases.
    2. The increase is mild and may occur after the fourth day of infarction, and the peak is reached in the next 4 days (another reference says 7 to 14 days after the infarction).
    3. A rise in GGT is seen in 5% to 30% of cases.
12. Alcohol ingestion. There is an average increase of >3.5 times the normal value.
    1. In the case of alcohol abuse, there is a GGT/Alkaline phosphatase ratio >2.5.
13. GGT is raised in EBV infection (Infectious mononucleosis), cytomegalic viral infection, and Reye syndrome.
14. There is an increase in drugs like Warfarin, Barbiturates, Valproic acid, Dilantin, and alcohol.

What is the cause of the decreased value of Gamma-glutamyl transferase (GGT)?

• Hypothyroidism.

Where will you see normal values of Gamma-glutamyl transfers (γ-GT)?

1. Bone disorder and bone growth.
2. Pregnancy.
3. Skeletal muscle disease.
4. Renal failure.

• GGT is the choice of enzyme in the case of Alcoholism.
• Very good at monitoring liver disease. Its return to normal in liver disease is an excellent indicator.

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