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Unit Code 460073:
Gamma-Glutamyltransferase (GGT), Serum

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Useful For

GGT measurement is principally used to diagnose and monitor

hepatobiliary disease. It is currently the most sensitive enzymatic

indicator of liver disease. GGT in serum can be used to ascertain

whether observed elevations of ALP are due to skeletal disease

(normal GGT) or reflect the presence of hepatolbiliary disease

(elevated GGT). GGT is also used as a screening test for occult

alcholism.

Clinical Information

Gamma-glutamyltransferase (GGT) is primarily present in kidney,

liver and pancreatic cells. Small amounts are present in other tissues. 

Even though renal tissue has the highest level of GGT, the enzyme

present in the serum appears to originate primarily from the hepatobiliary

system, and GGT activity is elevated in any and all forms of liver

disease. It is highest in cases of intra- or posthepatic biliary obstruction,

reaching levels some five to thirty times normal.  It is more sensitive

than ALP, NTP, leucine aminopeptidase, AST and ALT in detecting

obstructive jaundice, cholangitis and cholecystitis; its rise occurs

earlier than these other enzymes and persists longer. Only

modest elevations (two to five times normal) occur in infectious hepatitis,

and in this condition GGT determinations are less useful diagnostically

than are measurements of the transaminases. High elevations of GGT

are also observed in patients with either primary or secondary (metastatic)

neoplasms. Elevated levels of GGT are noted not only in the sera of

patients with alcoholic cirrhosis but also in the majority of sera from

persons who are heavy drinkers. Studies have emphasized the value

of serum GGT levels in detecting alcohol-induced liver disease. 

Elevated serum values are also seen in patients receiving drugs such

as phenytoin and phenobarbital, and this is thought to reflect induction

of new enzyme activity.

Reference Values

Males

      0-11 months:  not established

      1-6 years:  7-19 U/L

      7-9 years:  9-22 U/L

      10-13 years:  9-24 U/L

      14-15 years:  9-26 U/L

      16-17 years:  9-27 U/L

      18-35 years:  9-31 U/L

      36-40 years:  8-35 U/L

      41-45 years:  9-37 U/L

      46-50 years:  10-39 U/L

      51-54 years:  10-42 U/L

      55 years:  11-45 U/L

      > or = 56 years:  12-48 U/L

Females

      0-11 months: not established

      > or = 1 year:  6-29 U/L

Interpretation

An elevation of GGT activity is seen in any and all forms of liver

disease, although the highest elevations are seen in intra- or

posthepatic biliary obstruction. Elevated values can also indicate

alcoholic cirrhosis or individuals who are heavy drinkers. Normal

values are observed in various muscle disease and in renal failure. 

Normal values are also seen in cases of skeletal disease, children

older than one year and in healthy pregnant women--conditions in

which ALP is elevated. Thus, measurement of GGT in serum can be

used to ascertain whether observed elevations of ALP are due to

skeletal disease or reflect the presence of hepatobiliary disease.

Cautions

GGT activity is inducible by drugs such as phenytoin and

phenobarbital, and therefore, elevations should not be considered

indicative of liver disease until drug use is ruled out. Elevations are

also seen after ingestion of alcoholic beverages.

Clinical Reference

Tietz Textbook of Clinical Chemistry, Edited by CA Burtis, ER Ashwood. 

WB Saunders Company, Philadelphia, 1999

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