Interesting read on Liver Enzymes.

[DOGMA]

I thought this might be usefull for some of you.

Liver Enzymes

Four separate liver enzymes are included on most routine laboratory tests. They are- aspartate aminotransferase (AST or SGOT) and alanine aminotransferase (ALT or SGPT), which are known together as transaminases; and alkaline phosphatase (AP) and gamma-glutamyl transferase (GGT), which are known together as cholestatic liver enzymes. Elevations of these enzymes can indicate the presence of liver disease.



AST and ALT (Transaminases)

AST and ALT are jointly known as transaminases. They are associated with inflammation and/or injury to liver cells, a condition known as hepatocellular liver injury. Damage to the liver typically results in a leak of AST and ALT into the bloodstream.

Because AST is found in many other organs besides the liver, including the kidneys, the muscles, and the heart, having a high level of AST does not always (but often does) indicate that there is a liver problem. For example, even vigorous exercise may elevate AST levels in the body. On the other hand, because ALT is found primarily in the liver, high levels of ALT almost always indicate that there’s a problem with the liver. (Conversely, a normal ALT level does not necessarily mean that the liver is definitely normal- but, more about this later.)

Despite what one might expect, high levels of transaminases in the blood don’t always reveal just how badly the liver is inflamed or damaged. This is an extremely important point to keep in mind. The normal ranges for AST and ALT are around 0 to 40 IU/L and 0 to 45 IU/L respectively. (IU/L stands for international units per liter and is the most commonly accepted way to measure these particular enzymes.) But someone who has an ALT level of 50 IU/L is not necessarily in better condition than someone with an ALT level of 250 IU/L! This is because these blood tests measure inflammation and damage to the liver at an isolated point in time. For instance, if the liver is inflamed on the day that blood was drawn—let’s say if a patient consumes an alcoholic drink a few hours prior to blood being drawn—the levels of the transaminases may be much higher than if the alcohol had not been consumed. Following the same reasoning, if the liver was damaged years before—by excessive alcohol use—the results of a blood test done today may be normal, but a damaged liver may still be present.

To confuse issues even further, there are many other factors besides liver injury that could affect the levels of AST and ALT. For example, males have higher transaminase levels than females. And, African-American men have higher AST levels compared with Caucasian men. Even the time of day that a blood sample is drawn may influence the level of transaminase elevation. People appear to have higher transaminase levels in the morning and afternoon than in the evening. Food intake does not appear to have a significant effect on transaminase levels. Thus, levels do not significantly differ in the fasting and non-fasting state. Finally, transaminase levels may vary from day-to-day.

The ratio of the ALT and AST may also provide useful information regarding the extent and cause of liver disease. Most liver diseases are characterized by greater ALT elevations than AST elevations. Two exceptions to this rule exist. Both cirrhosis and/or alcohol abuse are associated with higher AST levels than ALT levels, often in a ratio of approximately 2:1.

Elevations of the transaminases occur due to so many causes that they give the doctor only a vague clue of the diagnosis. Additional testing is required in order to determine more precisely what is wrong with the liver. Some possible causes of elevated transaminase levels include the following:

• Viral hepatitis

• A fatty liver

• Alcoholic liver disease

• Drug/medication-induced liver disease

• Autoimmune hepatitis

• Herbal toxicity

• Genetic liver diseases

• Liver tumors

• Heart failure

- Strenuous exercise



GGT and AP (Cholestatic Liver Enzymes)

High levels of GGT and AP hint at a possible blockage of the bile ducts, or of possible injury to, or inflammation of, the bile ducts. This type of problem is characterized by an impairment, or failure, of bile flow, which is known as cholestasis. This type of liver injury is known as cholestatic liver injury, and this type of liver disease is known as cholestatic liver disease. (Primary biliary cirrhosis, discussed in Chapter 15, is an example of a cholestatic liver disease.) Intrahepatic cholestasis refers to bile duct blockage or injury within the liver. Intrahepatic cholestasis may occur in people with primary biliary cirrhosis or liver cancer (see Chapter 19), for example. Extrahepatic cholestasis refers to bile duct blockage or injury occurring outside the liver. Extrasyntherolhepatic cholestasis may occur in people with gallstones.

When a blockage or inflammation of the bile ducts occurs, the GGT and AP can overflow like a backed up sewer and seep out of the liver and into the bloodstream. These enzymes typically become markedly elevated—approximately ten times the upper limit of normal.

GGT is found predominantly in the liver. AP is mainly found in the bones and the liver but can also be found in many other organs, such as the intestines, kidneys, and placenta. Therefore, elevated levels of AP will indicate that something is wrong with the liver only if the amount of GGT is raised as well. Keep in mind that, GGT can be elevated without AP being elevated, as GGT is a sensitive marker of alcohol ingestion and certain hepatotoxic (liver toxic) drugs. It should be noted that for unclear reasons, people who smoke cigarettes appear to have higher AP and GGT than nonsmokers. Also, levels of AP and GGT are most accurate after a twelve-hour fast. You are beginning to get an inkling of the complexities that arise when evaluating abnormal LFTs!



Normal levels of AP range from 35 to 115 IU/L and normal levels of GGT range from 3 to 60 IU/L. Some causes of elevated AP and/or GGT include the following:

• Primary biliary cirrhosis

• Primary sclerosing cholangitis

• Nonalcoholic fatty liver disease (NAFLD)

• Alcoholic liver disease

• Liver tumors

• Drug-induced liver disease

• Gallstones


All contents of this article are Copyright © Melissa Palmer, MD

Melissa Palmer, MD is the author of " Dr. Melissa Palmer's Guide of Hepatitis and Liver Disease". (Published 2004. Penguin Putnam).

 

[JETHRO TULL]

Thanks for the post.

I read it and will continue to read articles like it every time.

 

[km2000]

very good read man, any newbies and anyone else woho needs to get blood work done, save this to your pc and print out a copy, it will help ya to understand the results!

 

[PHIL HERNON]

DOGMA

THANK YOU SO MUCH FOR THAT. IT BRINGS THIS SITE THAT MUCH MORE CREDIBILITY.

 

[Blitzkrieg]

Good read, thank you. I've always had elevated liver enzymes... doctors always told me it's nothing to worry about but when I started aas I got a little more concerned. This is good info...

 

[thebrick]

excellent. thank you.

 

[yautja]

great post.
i have slightly elevated ggt levels and this post explained why.
thanks

 

[bjjones]

Very informative, thanks!

 

[plat]

elevated liver enzymes

I've always had elevated liver enzymes...

Hi Blitzkrieg,

How are your elevated liver enzymes now - still at the high levels? Are you taking or have you taken anything for treatment of the elevated liver enzymes?

 

[BEASTZ6]

My liver enzymes are always way high. I need to have my gallblader removed because of some duct blockage, but I keep putting it off.

 

[MR. BMJ]

Thanks for the post and info!

BMJ

 

[garrithv]

good post. How would you accurately test for the state of liver then? multiple tests over a few days? some sort of scan?

 

[db006]

My liver enzymes are always way high. I need to have my gallblader removed because of some duct blockage, but I keep putting it off.

if your gallbladder ruptures, that can be fatal.

 

[Smith70592]

good post. How would you accurately test for the state of liver then? multiple tests over a few days? some sort of scan?

What is usually most helpful is serial testing of AST (SGOT) and ALT (SGPT) over time to determine whether the levels are increasing, remaining stable, or decreasing.

It is, therefore, worth mentioning that these liver enzymes do not give an indication of the function of the liver. Sometimes they are mistakenly referred to as “liver function tests” or LFTs, but it is a misnomer commonly used.


My Hepatologist told me bilirubin is the true indicator of how well the liver is functioning. Bilirubin results from the enzymatic breakdown of heme. Unconjugated bilirubin is conjugated with glucuronic acid in hepatocytes to increase its water solubility and is then rapidly transported into bile. The serum conjugated bilirubin level does not become elevated until the liver has lost at least one half of its excretory capacity. Thus, a patient could have obstruction of either the left or right hepatic duct without a rise in the bilirubin level.

Because the secretion of conjugated bilirubin into bile is very rapid in comparison with the conjugation step, healthy persons have almost no detectable conjugated bilirubin in their blood. Liver disease mainly impairs the secretion of conjugated bilirubin into bile. As a result, conjugated bilirubin is rapidly filtered into the urine, where it can be detected by a dipstick test. The finding of bilirubin in urine is a particularly sensitive indicator of the presence of an increased serum conjugated bilirubin level.

When a patient has prolonged, severe biliary obstruction followed by the restoration of bile flow, the serum bilirubin level often declines rapidly for several days and then slowly returns to normal over a period of weeks. The slow phase of bilirubin clearance results from the presence of delta-bilirubin, a form of bilirubin chemically attached to serum albumin. Because albumin has a half-life of three weeks, delta-bilirubin clears much more slowly than bilirubin-glucuronide. Clinical laboratories can measure delta-bilirubin concentrations, but such measurements are usually unnecessary if the physician is aware of the delta-bilirubin phenomenon.

With elevated bilirubin jaundice may occur. What essentially occurs is a buildup of bilirubin, which is formed when red blood cells break down. Since it cannot be excreted in the bile, it essentially backs up into the body and causes a yellowing of skin and eyes. This is not something you want to see.

 

[stonecold434]

Interesting information. I hadn't considered before that normal values on these tests are not a guarantee that all is well, more of a probability.