Today’s fact of the day will be in relation to the one we had yesterday regarding Australia's laws about kava. Today we’re going to focus on one piece of that and expand on it. This topic is liver tests and increased GGT.
GGT is short for gamma-glutamyltransferase. This is a liver enzyme that is tested for in a good majority of metabolism tests. GGT is present in the cell membranes of tissues including liver, kidneys, bile ducts, pancreas, heart, and brain. It is involved in the metabolism of glutathione and the detoxification of pharmaceutical compounds among hundreds of different functions. Introduced over 40 years ago, tests for quantification of this enzyme are commonly measured as a sensitive but not very specific liver function test (Whitfield 2001).
We should also address two other common terms seen when viewing a liver metabolic test and those are AST and ALT. Both are highly concentrated in the liver, however ALT is a more specific indicator of liver injury. Normal ranges of ALT are from 3-30 U/L. Liver damage with ALT will begin to indicate when levels reach 3 times the normal upper range. GGT can help confirm the origin of other elevated enzymes, or can help support the suspicion of alcohol use in patients (Fancher, Kamboj, and Onate 2017).
In 2007 a study was performed on predominantly Tongan individuals in Hawaii. 62 subjects were tested. Subjects were screened for compromising liver conditions prior to the tests such as hepatitis, and co-administration of drugs which may affect the liver. Participants which were regular kava drinkers were found 5 times more likely to have increased levels of GGT on metabolism tests. This number closely correlates to BMI in kava drinkers linearly. Increased BMI → Increased GGT. This study found no association between kava drinking and elevated AST and ALT values which classically indicate liver issues/damage. Aqueous kava was, in this study, considered a possible contributing factor to increased levels of GGT. This study goes on to say that GGT elevation in these kava drinkers may be an artifact of GGT induction, rather than a sign of liver toxicity (Brown et al. 2007).
Brown, Amy C., Janet Onopa, Peter Holck, Pakieli Kaufusi, Derek Kabasawa, Winston J. Craig, Klaus Dragull, Arieh M. Levine, and Jonathan D. Baker. 2007. “Traditional Kava Beverage Consumption and Liver Function Tests in a Predominantly Tongan Population in Hawaii.” Clinical Toxicology 45 (5): 549–56.
Fancher, Tonya, Amit Kamboj, and John Onate. 2017. “Interpreting Liver Function Tests.” Current Psychiatry 6 (5): 61–68.
Whitfield, J. B. 2001. “Gamma Glutamyl Transferase.” Critical Reviews in Clinical Laboratory Sciences 38 (4): 263–355.