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Is Liver Enzymes (ALT, AST, CK) Height Normal in Athletes

Tuesday, September 7, 2021

In many different mediums, including in the emergency department, people ask me about the severity of elevated liver enzymes (ALT, AST) and CK after exercise.

I feel the need to provide information on this issue, which cannot be understood as a matter of fact. Because it is an important issue whether these values, which increase after intense exercise, require intervention.

In this article, I will talk about ALT, AST and CK values in athletes and their importance.

What are ALT, AST and CK?

I would like to explain exactly what these values ​​mean before examining alt, AST and CK in athletes. So you can adapt to the subject more easily.


This substance, which stands for alanine aminotransferase, is a catalyst involved in the alanine cycle in your body. Its task is to move an amino group in the alanine amino acid to alpha ketoglutarate.

Although it is generally found in liver tissue, it is also found in small amounts in several different tissues in the body.


Aspartate aminotransferase, this substance is a catalyst involved in the aspartate cycle in your body. Its task is to accelerate the conversion of aspartate in your body into several different building blocks.

Like ALT, AST is generally found in liver tissue but is also found in a few different tissues.

As you can see, ALT and AST are not specific to a single tissue, but most of them are found in the liver. This is why we often associate elevations of ALT and AST with liver damage.


This enzyme, which stands for creatine kinase, mediates the conversion of creatinine to phosphocreatine in your body. This enzyme plays an important role in energy consumption and metabolic processes.

The most important of these forms is CK-MB, which is found more in heart muscle than other forms. Because troponin and CK-MB levels are a common unit in the diagnosis of cardiac problems.

Can athletes increase ALT, AST and CK levels due to exercise and can this height be misinterpreted? My answer is yes. Like many subjects of athletes, laboratory results should be evaluated differently.

I have compiled researches, studies and results for you. Let’s examine it.

ALT, AST and CK height in athletes

ALT and AST values ​​are really a parameter that needs attention. Because it often increases with liver-induced problems. This is actually the only issue that misleads physicians about athletes.

For this reason, the athletes are experiencing serious problems in the medical examination.

Is it possible to experience ALT, AST and CK elevation only due to sport without any reason?

Fifteen healthy men participated in the study to investigate exercise and alteration of ALT, AST, CK values. Before the study, ALT, AST and CK values ​​in the reference range, no disease and no drug use during the study participants are evaluated.

In the study, ALT, AST and CK values ​​of the athletes who applied one hour of moderate-weight conventional weight training are monitored for a week in the post-training period.

The results show that ALT, AST and CK levels increase by an average of 2-5 times compared to baseline levels, followed by a slow fall and return to normal levels for seven days.

The levels of billuribine, ALP and GGT were normal throughout the study.

Another important point was that these increases did not cause any complaints.

As a result, the increase in ALT, AST and CK values ​​of individuals in moderate and high intensity exercises is expected and not abnormal.

Are elevating liver enzymes harmful in athletes?

Actually, that’s the question we’ve been facing all along. Because if your liver is really damaged, you should stop and find the problem no matter what.

There is one point to understand here. Elevation of liver enzymes (especially non-liver specific ALT, AST) does not directly describe liver damage.

Many different conditions, from hyperthyroidism to genetic causes, cause ALT and AST to rise and / or elevate, but do not cause liver damage.

The only reason for this is that ALT and AST are not directly linked to the liver. ALT and AST in many different tissues may also be elevated due to a common exercise condition such as muscle damage.

Here we need to find a good way to distinguish real liver damage from exercise-induced liver enzyme elevation. Because ALT and AST increase only due to muscle damage, there is nothing to fear.

As you can see in the first study, GGT, which is related to liver and more important value, was counted in place as well as exercise-induced ALT and AST elevation. Actually, it’s not a coincidence. Because if ALT and AST elevation is exercise-induced, GGT will remain constant, but GGT may increase in case of liver disease.

In contrast to the first study, ALP and billuribine levels may increase minimally in continuous and severe exercises.

So what do I do?

You are doing sports and during a routine check ALT, AST and CK are high. What do you need to do? First of all, don’t worry, my clinical practice shows that ALT and AST values ​​may be high, especially in newcomers.

ALT and AST may also increase in individuals who have been exercising for a long time. But we’re less common than beginners.

First, CK increases due to muscle damage and is absolutely not significant. If you do not have cardiovascular disease and no chest pain, it can be confirmed that there is no problem after a simple ECG.

Your ALT and AST levels may increase due to muscle damage. We talked about this in the rest of the article. If such a situation is encountered, more specific tests such as GGT, billuribine and ALP should be requested.

In addition, other problems that may cause liver damage – the most common drug-induced, viral-related causes (such as hepatitis) – should be excluded.

After that, the results should be evaluated and if the GGT, billuribine and ALP values ​​are normal, ALT and AST values ​​should be re-evaluated at the end of one week after exercise, without using medication.

But the practice of medicine is not always clear. The individual’s condition, suspected diseases and many other conditions can change the physician’s perspective. Therefore, you should always trust your physician and act with him.

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