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All About Your Liver Function

A comprehensive guide to healthy liver function, the signs of liver disease and how a liver function test helps you identify issues.

What Is The Liver?

The liver is the largest organ of the body, weighing as much as 1500 grams in an adult and comprising 2.5 % of the total body weight. It is located below the diaphragm in the abdominal cavity, extending from the right fifth rib to the lower border of the rib cage.

The liver is composed of two anatomical lobes - namely the much larger right lobe and the smaller left lobe. There are several further subdivisions of the lobes of the liver, with the main working cells of the liver known as hepatocytes. Hepatocytes have a unique ability to regenerate in response to liver injury.

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What Is The Function of the Liver?

The liver is a vital organ which performs an astonishingly large number of tasks. These impact all body systems. The major liver functions are detailed as follows:

1. Synthesis

Many compounds, including proteins (albumin, globulins), cholesterol, triglycerides, and lipoproteins are all created in the liver, for use throughout the body.

Bile juice production is also one of the important functions of the liver. Bile helps in the digestion and absorption of fat molecules from the diet.

2.Metabolism

Metabolism refers to the continual chemical processes that occur in your body. In the liver, this includes the following functions:

  • Carbohydrate metabolism: The liver performs the glycogen metabolism and helps with the maintenance of normal blood glucose levels.
  • Lipid metabolism: cholesterol metabolism, bile acid synthesis, and metabolism of lipoproteins all occur within the liver.
  • Protein metabolism: The liver is the site for formation as well as the breakdown of the protein molecules in the body. 

3. Detoxification and excretion

The liver plays a key role in the detoxification of harmful molecules like ammonia (to urea via the urea cycle), bilirubin, cholesterol, and drug metabolites. These detoxified molecules are excreted from the body as bile and in urine.

4. Storage Function

Vitamins and minerals are essential nutrient elements to the body. Various vitamins like Vitamin A, D, E, K, and B12 which are absorbed from the intestines are carefully stored by the Liver.

Glycogen and the trace element iron (as ferritin) are also stored in the liver.

In addition to specific compunds, the liver also acts as a reservoir of blood volume in the body.

5.Hematological function:

Finally the liver also plays a crucial role in blood clotting, producing clotting factors like Factor V and Factor VII.

Fibrinogen which is involved in blood coagulation is also synthesized in the liver. 

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What Are The Symptoms of A Liver Disorder?

As detailed above, there are a wide range of liver functions. As such, a person suffering from liver disease can have numerous complaints or may have no complaints at all.

Not every patient suffers from the same clinical problem and also, it is not necessary for every symptom to be present in every patient. 

Diagnosing a case of liver disease can be difficult. However, many patients with liver disease have some classic symptoms which include:

  • Abdominal distension and pain over the right upper quadrant of the abdomen.
  • Jaundice –  a yellowish discoloration of the body.
  • Altered sleep, fatigue and weakness.
  • Clay-colored stools or highly coloured urine.
  • Nausea, vomiting and very bad breath.
  • Disturbed consciousness, personality changes or intellectul disturbance.
  • Easy bruising, intense Itching, or thinning of the skin.
  • Anorexia, weight loss and muscle wastage.
  • Lower limb edema (swelling).

If you have any of these liver disease symptoms it is recommended to discuss them with your doctor. As detailed below, they may request a liver function test and look for additional signs of illness.

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What Are The Signs of Liver Disease?

When a patient visits a doctor with the above-mentioned symptoms, the doctor will perform a detailed examination, looking for various clues that can lead to a prompt diagnosis. The more of these signs are present the more it points towards liver disease. 

These signs which are seen by a physician are listed according to the body parts and are as follows:

  • In the Head and Neck:
    • Alopecia (Hairfall),
    • Subconjunctival hemorrhage (Bleeding into the conjunctiva).
    • Pale skin and face.
    • Keyser-Fleischer Ring – Dark ring encircling the iris of the eye.
    • Swelling of the parotid gland.
    • Loss of Upper Eyebrow (Supraciliary madarosis).
    • Spider naevi – Swollen blood vessels are seen beneath the skin looking like a spider’s web.
  • In  the Chest:
    • Breast enlargement in males (Gynecomastia).
    • Spider naevi (as above).
    • Scratch marks due to intense itching.
    • Loss of body hair.
  • In the upper limbs:
    • Swelling of soft tissues under the nail bed (Clubbing).
    • Whitish discoloration appearing on nails (Leuconychia).
    • Bruising.
    • Tremor of the hand when the wrist is extended (Flapping tremor).
    • Permanent bending of fingers (Dupuytren’s contracture).
    • Redness of palms of both hands (Palmar erythema).
  • In the abdomen:
    • Scars.
    • Distension of Abdomen.
    • Enlargement of veins which are seen radiating outward from Umbilicus (Caput medusa).
    • Enlargement of Liver (Hepatomegaly).
    • Enlargement of Spleen (Splenomegaly).
    • Building up of fluid in the abdomen (Ascites).
    • Palpable Gall Bladder.
  • In lower limbs:
    • Painless swelling of both legs.
    • Easy bruising.
    • Scratch marks due to intense itching.

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What Is A Liver Function Test?

The Liver function test (LFT) is a group of blood tests that together measure:

  1. substances that the liver produces, and
  2. substances that are released when the liver is damaged. 

This provides a highly sensitive screening tool that helps to determine the health of your liver by measuring the levels of proteins, liver enzymes, and bilirubin in your blood.

The use of liver function tests is also highly specific when more than one test is performed and is found to be abnormal.

In simple words, a liver function test is a non-invasive method to detect whether there is an abnormality in the function of the liver. These tests can assess how severe is the liver damage and also helps to predict an outcome on follow-up.

How To Take A Liver Function Test?

Liver Function testing is a quick and straightforward procedure to assess the status of the liver using a blood sample. Traditionally, this would be using a full-size blood sample collected from a large vein in the arm by a healthcare professional.

Advances in laboratory analysis have led to less blood being needed for testing, and it is now possible for a home liver function test to be conducted using a finger-prick blood sample (AKA Capillary blood).

In both cases the blood sample is sent to a laboratory for analysis. It usually takes 1-2 days for the report to be completed.

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Why Take a Liver Function Test?

Liver Function tests do not often identify the underlying cause, but abnormal results allow you and your doctor to plan any next steps. Together with the clinical history and physical examination they can be used to give an accurate diagnosis of the specific liver disorder. 

Liver function tests are often recommended in the following situations:

  • If a patient is experiencing the symptoms of a liver disorder.
  • If the patient has certain medical conditions including high blood pressure, diabetes as high triglycerides, diabetes, high blood pressure, or anemia.
  • If the patient consumes excess alcohol. Cirrhosis ranks as the 11th leading cause of death around the world.
  • To check for damage from liver infections, such as hepatitis B and hepatitis C.
  • To monitor side-effects of certain medications that are known to affect the liver.
  • If the patient has been diagnosed with gall bladder disease.
  • To monitor the disease and to understand how well the treatment is working.

Note that many liver diseases may be associated with normal levels of liver function tests. Likewise, abnormal levels of liver function tests may be found in otherwise asymptomatic healthy individuals. If symptoms persist, a full clinical investigation is required.

What Does A Liver Function Test Measure?

Three groups of biomarker can be tested in a LFT panel, summarized as follows:

  1. Bilirubin tests
    1. Serum bilirubin test
  2. Liver Protein Tests:
    1. Albumin levels
    2. Globulin levels
    3. Albumin to globulin ratio
    4. Prothrombin time
  3. Liver Enzyme Tests:
    1. Alkaline Phosphatase test (ALP)
    2. Alanine Aminotransferase test (ALT)
    3. Aspartate Aminotransferase test (AST)
    4. Gamma glutamyl transferase test (GGT)

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Let’s explore each of the tests that can be included in a liver function blood test in detail:

Bilirubin Testing

This is the main bile pigment and is the by-product of Red Blood cell breakdown. The bilirubin level in the body is a careful balance between production and degradation of the pigment in the body. The liver is involved in the uptake of unconjugated bilirubin (water-insoluble) and then it conjugated it to form water-soluble bilirubin which is excreted in the bile. 

What Makes Bilirubin Levels High?

High bilirubin levels are observed in:

  • Mild elevation:
    • Liver Diseases
    • Physiological jaundice
    • Inherited cases of hyperbilirubinemia
  • Moderate elevation:
    • Obstruction in the flow of Bile Juice outside the Liver (Extrahepatic obstruction, also known as Obstructive Jaundice).
    • Obstruction in the flow of Bile Juice inside the Liver (Intrahepatic Cholestasis).
    • Viral hepatitis
    • Inherited cases of hyperbilirubinemia

The most familiar issue of high biirubin is as the yellowish pigment observed in jaundice.

How Is Bilirubin Measured?

A bilirubin test can check bilirubin levels in several forms:

  • Total Bilirubin - the total amount of direct and indirect bilirubin
  • Direct (conjugated bilirubin) – the water-soluble fraction of total bilirubin
  • Indirect (Unconjugated Bilirubin) – calculated as the difference between the Total Bilirubin and the direct Bilirubin.

 

What Are The Normal Levels Of Bilirubin?

  • Total Bilirubin: 0.2 – 0.8 mg/dL
  • Unconjugated (Indirect): 0.2 – 0.7 mg/dL
  • Conjugated (Direct): 0.1 – 0.4 mg/dL

 
What Levels of Bilirubin Are Concerning (Pathological)?

  • Plasma Bilirubin level > 1 mg/dL indicates Increased Bilirubin (Hyperbilirubinemia).
  • Levels between 1 and 2 mg/dL indicate Latent Jaundice.
  • Level more than 2 mg/dL produces Clinical Jaundice.

 

Serum Albumin (Liver Protein Test)

Albumin is the most abundant protein in the body and is synthesised by the liver. Synthesis of albumin depends on the number of functioning liver cell mass.

Albumin is normally present at a level of 3.5 – 5 g/dL. Corticosteroids and Thyroid hormones stimulate albumin synthesis, so they may be responsible for increased albumin levels in the blood.

Levels may be normal in cases like acute viral hepatitis, drug-related hepatotoxicity, and obstructive jaundice.

Its level is decreased in all chronic liver diseases. However, a decreased level of albumin is not specific only for liver diseases. They also are decreased in cases like:

  • Protein malnutrition.
  • Nephrotic syndrome.
  • Chronic protein-losing enteropathies.

Serum Globulin (Liver Protein Test)

Serum globulins make up the remainderr of blood proteins, and exist in several different forms, including immunoglobulins and enzymes.

Normal levels of serum globulin are 2.5 – 3.5 g/dL, with high levels seen in:

  • Autoimmune Hepatitis (where autoantibodies are produced against the liver hepatocytes).
  • Alcoholic Liver Disease.
  • Chronic Hepatitis.
  • Cirrhosis (Condition where normal liver tissue is repalced by scar tissue and indicates permanent damage).

Prothrombin time (PT) (Liver Protein Test)

Prothrombin is a protein which helps in clotting of the blood, is synthesised by the liver and is a marker of normal liver function.
It indicates the present state of liver function, however, it is not specific to liver diseases.

The prothombin time test is the time taken for clotting to take place in a plasma that has been citrated (where an optimum quantity of Thromboplastin and Calcium have been added).

What Is A Normal Prothrombin time?

  • The normal prothombin time is 10 to 14 seconds.

What Are Abnormal Prothombin Times?

The prothrombin time value is increased only when the liver loses more than 80 percent of its capacity.

Prothrombin time (PT) increase is seen in conditions such as:

  • A severe parenchymal liver disease that causes decreased synthesis of Prothrombin.
  • Vitamin K deficiency.
  • Deficiency of clotting factors
  • Disseminated Intravascular Coagulation (DIC)
  • Ingestion of certain drugs

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Alkaline Phosphatase (ALP) Blood Test

ALP is an enzyme mainly found in the liver and bone tissue. Alkaline Phosphatase performs lipid (fat) transport in the intestine and aids in bone calcification.

ALP is also a marker of liver function. In the liver, it is normally found within the cell. Whenever the liver is injured or infected or damaged the enzyme spills out in the blood. This causes an increased blood level of ALP.

What Are Normal ALP Levels?

•    Normal levels: 41 – 133 IU/L.5

What Causes Abnormal Alkaline Phosphatase Levels?

Elevated levels are seen in:

  • Moderate elevation in the level of ALP:
    • Infection of the liver (Infective hepatitis).
    • Excessive consumption of Alcohol (Alcoholic Hepatitis).
    • Cancer of Liver (Hepatocellular Carcinoma).
    • Peripheral Arterial disease
  • High Levels:
    • Obstruction in the flow of Bile Juice outside the Liver (Extrahepatic obstruction, also known as Obstructive Jaundice).
    • Obstruction in the flow of Bile Juice inside the Liver (Intrahepatic Cholestasis).
  • Very High Levels:
    • Bone diseases.
    • The third trimester of asymptomatic normal pregnancy (due to extra production from the placental tissue)

Low levels of ALP are less common and are seen in:

  • Hypothyroidism
  • Pernicious anemia
  • Zinc deficiency
  • Congenital hypophosphatasia

Alanine Aminotransferase (ALT) Blood Test


ALT is also found in the kidney, heart, muscle but a greater concentration is found in the liver compared with other tissues of the body. 

As such ALT is more specific to liver function than Aspartate Aminotransferase, and issues can be detected in the blood many days before clinical signs appear.

What Are Normal ALT Levels?

•    Normal levels: 7 – 56 IU/L2

What Causes Abnormal Alanine Aminotransferase Levels?

High levels of ALT are seen in:

  • Minor elevation:
    • Cirrhosis, Hepatitis C, and Non-Alcoholic Steatohepatitis (50 – 100 IU/L).
  • Moderate elevation:
    • Alcoholic Hepatitis (100 – 300 IU/L)
  • Very high levels:
    • Acute Hepatitis, Ischemic Liver Injury, Toxin-induced liver damage (300 – 1000 IU/L)

  
    Note that obese but otherwise normal individuals may have high enzyme levels.   ALT level may be normally elevated during the 2nd trimester of pregnancy in otherwise, asymptomatic normal pregnancy.

Aspartate Aminotransferase (AST) Blood Test

AST is a marker of hepatocellular (liver cell) damage, although it can also be released with heart, muscle, and brain disorders and is less specific to liver disease.

What Are Normal AST Levels?

•    The normal range is: 0 – 35 IU/L2

What Causes Increased AST Levels?

High serum levels are seen in:

  • Chronic Hepatitis
  • Cirrhosis
  • Hepatocellular Carcinoma
  • It is also found elevated in an asymptomatic pregnant patient who present with pre-eclampsia.

AST/ALT Ratio (Liver Enzyme Test)

The ratio is of more clinical importance than the assessment of individual elevated levels of ALT or AST.

Elevated AST/ALT ratio is seen in:

  • Liver Fibrosis
  • Viral Hepatitis
  • Alcoholic Hepatitis
  • Non-alcoholic Fatty Liver Disease
  • Wilson’s Disease
  • Hyperthyroidism

The ratio is reversed ( i.e. ALT is more than AST) in:

  • Toxic hepatitis
  • Some cases of Viral hepatitis
  • Chronic Active hepatitis
  • Cholestatic Hepatitis

Gamma-glutamyltransferase (GGT) Blood Test

This enzyme is widely distributed in body tissues including liver cells (hepatocytes). It is a sensitive index to assess liver abnormality.

What Are Normal Levels of GGT?

  • Normal Level of GGT is 9 to 85 U/L.5

What causes Increased AST Levels?

Levels of AST are elevated in:

  • Infective hepatitis
  • Prostate Cancer
  • Alcoholics

Certain Non-hepatic causes also cause elevated GGT levels, like:

  • Uncomplicated Diabetes Mellitus
  • Acute Pancreatitis
  • Myocardial Infarction
  • Anorexia Nervosa
  • Hyperthyroidism
  • Obesity
  • Use of drugs like Phenobarbitone, Phenytoin, Paracetamol and certain Antidepressant drugs.

GGT is also a highly sensitive indicator of alcohol abuse (where GGT levels are elevated more than 10 times).

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Other Liver Function Tests

There are other tests as well to assess liver function. They are not routinely performed but are done under specific conditions. Vitall do not offer these liver function tests for home use but for completeness they are outlined below:

Nucleotidase (NTP):

NTP is found throughout the body tissues, with increased blood levels seen in:

  • Obstructive jaundice
  • Parenchymal liver disease
  • Hepatic metastasis from other diseases
  • Bone disease
  • Hepatic tumors
  • Viral hepatitis
  • Chronic hepatitis
  • Second and third trimesters of pregnancy

Ceruloplasmin

Ceruloplasmin is synthesized in the liver and is a major carrier of copper in the blood. It is the most reliable test to differentiate between chronic alcoholic liver disease and Wilson’s disease.

Elevated levels are seen in:

  • Infections
  • Rheumatoid arthritis
  • Pregnancy
  • Obstructive jaundice

Levels are decreased in conditions like:

  • Kwashiorkor
  • Marasmus
  • Protein-losing enteropathy
  • Copper deficiency
  • Wilson’s disease
  • Neonates

α- fetoprotein (AFP)

AFP is highly active in the fetal liver and its level is depressed after birth.  It is the major serum protein in a developing fetus.
 

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Article Reviewed By

Doctors, Scientists & Experts Delivering Private Blood Testing Online

Dr. Kate Bishop |Chief Scientific Officer

Kate qualified with a BSc (Hons) in Biochemistry from the University of Birmingham in 1999. She then went on to study for a PhD in Biochemistry, before progressing as College Research Business Development Manager. In addition to her role within Vitall she is currently the director of operations at the College of Medical and Dental Sciences.

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All About Your Liver Function: References & Citations


1.    Thapa BR, Walia A. Liver function tests and their interpretation. The Indian Journal of Pediatrics. 2007 Jul 1;74(7):663-71.
2.    Gowda S, Desai PB, Hull VV, Math AA, Vernekar SN, Kulkarni SS. A review on laboratory liver function tests. The Pan African Medical Journal. 2009;3.
3.    Giannini E, Botta F, Fasoli A. et al. Progressive liver functional impairment is associated with an increase in AST/ALT ratio. Dig Dis Sci. 1999;44:1249–1253.
4.    Sorbi D, Boynton J, Lindor KD. The ratio of aspartate aminotransferase to alanine aminotransferase: potential value in differentiating nonalcoholic steatohepatitis from alcoholic liver disease. Am J Gastroenterol. 1999;94:1018–1022.
5.    Diana Nicoll C. In: Current medical diagnosis and treatment. 46th edition. Stephen JM, Maxine AP, editors. Mc Graw hill; 2007. Appendix: Therapeutic drug monitoring and laboratory reference ranges; pp. 1767–1775.
6.    Mauro P, Renze B, Wouter W. In: Tietz text book of clinical chemistry and molecular diagnostics. 4th edition. Carl AB, Edward R, David EB, editors. Elsevier; 2006. Enzymes; pp. 604–616.
7.    LaRusso NF, Summerskill WH, McCall JT. et al. Abnormalities of chemical tests for copper metabolism in chronic active liver disease: differentiation from Wilson's disease. Gastroenterology. 1976;70:653–655.
8.    Grizzi F, Franceschini B, Hamrick C. et al. Usefulness of cancer-testis antigens as biomarkers for the diagnosis and treatment of hepatocellular carcinoma. J Transl Med. 2007;5:3.
 

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