A group of liver function tests are often performed as part of routine laboratory testing. However, as you will learn in this article, these tests may also highlight dysfunction or disease in systems other than the liver.

As a Functional Medicine practitioner, I don’t rely solely on the results of one specific test. I also carefully evaluate your symptoms, diet, lifestyle, history, and other lab test results to further narrow down all potential sources of dysfunction or disease.

When interpreting results, Functional Medicine considers “optimal” ranges as opposed to “normal” ranges (learn more here). This allows us to identify and treat signs of dysfunction before a full-blown disease occurs.

Liver Dysfunction

When combined, the tests described below provide insight into how well (or poor) your liver is functioning. And it’s important to recognize that your diet and lifestyle are two key factors that affect liver function. For example, when the liver is overburdened with toxins, it may become congested. As a result, toxins may build up in your body and lead to additional problems.

Some common signs and symptoms of liver dysfunction include:

  • Abnormal cholesterol levels
  • Gas and bloating
  • Dietary fat intolerance
  • Constipation
  • Fatigue and weakness
  • Blood sugar imbalances
  • Brain fog
  • Depression
  • Poor memory
  • Food allergies
  • Skin rashes
  • Hormonal imbalances
  • Severe menopause or PMS
  • Liver spots (brownish spots on skin)

Thus, if liver dysfunction is suspected, Functional Medicine attempts to identify and eliminate all possible sources.

Common Liver Function Tests

Below are descriptions of the most common liver function tests performed.

Albumin

Albumin is a protein synthesized and secreted by the liver. And it’s the most abundant protein found in human blood. It plays a role in balancing fluids, transporting nutrients and hormones, metabolism, pH balance, blood vessel health, and fighting free radical damage.

The rate of albumin synthesis depends on liver function as well as nutritional intake. Specifically, the body needs a source of energy and amino acids (building blocks of protein) to manufacture albumin.

Thus, abnormal albumin levels may indicate a variety of potential problems in addition to liver dysfunction.

Decreased albumin levels are typically associated with:

  • Liver dysfunction
  • Systemic inflammation
  • Nutrient deficiencies
  • Digestive dysfunction

Elevated albumin levels may be a sign of dehydration.

Total Protein

The total protein test measures both albumin and globulins, which combined make up a majority of blood proteins.

Globulins are synthesized and secreted by both the liver and the immune system. Similar to albumin, energy and amino acids are required. And one of the key roles is to transport minerals, hormones, and fats throughout the body.

However, one very important type of globulins are known as immunoglobulins (a.k.a. antibodies), which play a crucial role in preventing infections and neutralizing toxins.

Decreased total protein levels may be a sign of:

  • Liver dysfunction
  • Nutrient deficiencies
  • Digestive dysfunction
  • Kidney dysfunction

Elevated total protein levels may be associated with:

  • Systemic inflammation
  • Chronic infections (i.e., viral hepatitis and HIV)
  • Bone marrow disorders
  • Dehydration

However, it’s worth noting that an optimal total protein level may still be detected even if albumin or globulin levels are out of range. Thus, it’s essential to consider albumin levels when interpreting total protein levels.

Albumin/Globulin Ratio (A/G Ratio)

Total protein and albumin are often used to calculate the ratio of albumin to globulins.

A low A/G ratio may be a sign of:

  • Liver dysfunction
  • Autoimmune disease
  • Kidney dysfunction

A high A/G ratio may indicate low levels of immunoglobulins, which are observed with genetic related disorders and leukemias (blood cancer).

Bilirubin

Bilirubin is a waste product created from the degradation of old red blood cells. And it’s the liver’s job to process bilirubin in a way that makes it easy for the body to eliminate.

There are two tests associated with bilirubin – total bilirubin and direct bilirubin.

Total bilirubin measures both indirect bilirubin (prior to liver processing) and direct bilirubin (after liver processing). However, as with total protein, total bilirubin doesn’t provide a complete picture.

Thus, direct bilirubin levels are also measured. And indirect bilirubin levels can then be calculated.

Elevated levels of indirect bilirubin may be a sign of:

  • B12 deficiency
  • Liver cirrhosis
  • Oxidative stress
  • Autoimmune disease
  • Hemolysis (premature destruction of red blood cells)

Elevated levels of direct bilirubin may be associated with:

  • Liver dysfunction
  • Viral hepatitis or other liver infections
  • Alcohol induced liver disease
  • Gallstones
  • Cholecystitis (inflammation of the gall bladder)
  • Liver tumors

Liver Enzyme Tests

The remaining three tests below evaluate blood levels of specific enzymes that reside in the liver. However, it’s worth noting that these enzymes are also found in other tissues within the body. Thus, these tests provide insight into a variety of potential issues, especially when evaluated together along with other laboratory tests.

Alkaline Phosphatase (ALP)

Alkaline phosphatase is found in the liver as well as the bones, skin, and digestive tract.

Elevated levels of ALP may be a sign of:

  • Viral hepatitis or other liver infections
  • Liver cirrhosis
  • Liver tumors
  • Fatty liver disease
  • Bone disorders
  • Leaky gut (increased intestinal permeability)
  • Shingles
  • Gallstones
  • Cholecystitis (inflammation of the gall bladder)

The activity of ALP is highly dependent on the presence of the mineral zinc. Thus, while low levels of ALP are optimal, abnormally low levels of ALP may be associated with a zinc deficiency.

Aspartate Aminotransferase (AST)

Aspartate aminotransferase is an enzyme found in the liver as well as the heart, muscles, kidneys, lungs, and pancreas. It is released into the bloodstream as a result of cellular damage or destruction.

Thus, elevated levels of AST may be a sign of:

  • Liver dysfunction
  • Cellular damage (in heart, liver, pancreas, muscle tissue)
  • Heart dysfunction or disease
  • Infectious disease

The functionality of AST heavily relies on the presence of vitamin B6. Thus, while low levels of AST are optimal, abnormally low levels of AST may be associated with a vitamin B6 deficiency, which can be caused by alcoholism.

Alanine Aminotransferase (ALT)

Alanine aminotransferase is found mostly in the liver, but smaller quantities are also found in muscle, kidney, and heart tissue. As with AST, it is released into the blood when cells are damaged or destroyed.

Thus, elevated levels of ALT may be associated with:

  • Liver dysfunction
  • Fatty liver disease
  • Viral hepatitis or other liver infections
  • Alcohol induced liver disease
  • Liver cirrhosis
  • Cellular damage (in liver, heart, or kidney tissue)

Similar to AST, abnormally low levels may be a sign of a vitamin B6 deficiency, which can be caused by alcohol abuse. In addition, abnormally low levels may also be associated with very a early stage of fatty liver disease.

In Conclusion

The liver function tests discussed above provide valuable information related to the health of your liver. However, the test results must be interpreted carefully. In addition, many factors and other laboratory tests must also be considered before drawing any conclusions.

Thus, if you suspect your liver isn’t functioning at top speed, functional medicine can help. We’ll look for signs and symptoms starting with a series of laboratory tests as well as thorough data analysis.

If dysfunction is detected, we’ll work closely together to identify and correct all possible sources. While this process will improve your liver function, it will also most likely improve your health in many other ways.

References

  1. Giannini, E. G., Testa, R., & Savarino, V. (2005). Liver enzyme alteration: a guide for clinicians. CMAJ : Canadian Medical Association Journal, 172(3), 367–379. http://doi.org/10.1503/cmaj.1040752
  2. Laker, M. F. (1990). Liver function tests. BMJ : British Medical Journal, 301(6746), 250–251.
  3. Limdi, J. K. (2003). Evaluation of abnormal liver function tests. Postgraduate Medical Journal,79(932), 307-312. doi:10.1136/pmj.79.932.307
  4. Weatherby, D., & Ferguson, S. (2002). Blood chemistry and CBC analysis: clinical laboratory testing from a functional perspective. Jacksonville, OR: Bear Mountain Pub.
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