Liver function can be assessed by reviewing various markers on a standard blood test. These markers are reflected in the primary metabolic enzymes. In truth, these enzymes can reveal more than just liver function. In fact, because of their presence in other locations besides the liver, various metabolic enzymes can reveal the function of other organs and systems of the body. Such an investigation is outside of the scope of this article.
Last week, I wrote an article that discussed many of the primary functions of the liver.To summarize, your liver has more than 500 critical biological functions, many of which can be impeded if the liver is not functioning correctly.
Various factors on a blood test can provide insight into liver function, such as:
- LDH (lactate dehydrogenase)
- AST (aspartate aminotransferase)
- ALT (alanine aminotransferase)
- GGT (gamma glutamyl transferase)
- ALP (alkaline phosphatase)
It is important to understand that more of a “Functional” interpretation of blood chemistry is necessary in order to obtain the most information.Many conventional laboratory reference ranges are statistical averages which do not necessarily reflect healthy or normal values.
Bilirubin is a waste product. It is the result of the breakdown of hemoglobin. Bilirubin is transported by spleen and bone marrow cells to the liver where it is then conjugated and excreted through bile. If ‘Total Bilirubin’ is elevated greater than 1.2, expect some sort of liver dysfunction or possible biliary tract obstruction. This should be correlated with other blood chemistry values.
Triglycerides are fats in your blood which serve as a source of fuel for all of the muscles of the body. High or low triglycerides are indicative of numerous metabolic problems as well as potential risk factors. Triglycerides values on a fasting blood test are synthesized by the liver. Consider that a triglyceride level greater than 110 may reflect fatty liver and/or liver congestion. This should be correlated with other values.
LDH (lactate dehydrogenase)
LDH is a group of metabolic enzymes that reflect carbohydrate metabolic activity. LDH is found in virtually all tissues of the body. So elevated LDH levels have limited value. LDH is often elevated >200 when there is congestion in the liver. If this is the case, one may see elevated bilirubin, ALP (alkaline phosphatase), ALT, GGT and AST may also be elevated as well in liver congestion and/or dysfunction.
ALT (alanine aminotransferase)
ALT is another metabolic enzyme that is found in liver, muscle, heart and kidney cells. High levels of this enzyme will be released into the bloodstream when there is damage to these specific cells. ALT levels of 35 or greater tend to indicate various stages of liver dysfunction and liver breakdown. ALT results should be correlated with other blood chemistry factors.
AST (aspartate aminotransferase)
AST is less of a sensitive metabolic enzyme for the assessment of liver issues. It is more often found elevated (>35) among those with cardiovascular risk factors. Nonetheless, elevated AST may indicate damage to the liver if correlated with other blood chemistry factors such as ALT, ALP, GGT and LDH.
GGTP (gamma glutamyl transferase)
GGT is a metabolic enzyme found chiefly in liver cells and therefore is a sensitive factor for assessing liver damage. It is very common that GGT levels will be elevated with regular alcohol consumption. Since pharmaceutical drugs also tend to have a toxic effect on the liver, it is common to see elevated GGT levels with those on prescription medications. GGT levels greater than 30 strongly correlate with hepatic-related issues.
ALP (alkaline phosphatase)
Typically ALP levels greater than 100 can be found correlative with varying degrees of liver dysfunction. ALP is a metabolic enzyme found in bone, intestines and liver. Therefore, abnormal values may correlate with numerous dysfunction. If ALP is found to be greater than 100 in adults, suspect that liver issues exist, especially if correlated with high levels of GGT and ALT.
ALP is an age-dependent enzyme. Children experience higher values of this enzyme because they are growing.