Elevated liver function tests (LFTs) or enzymes suggest that there may be some inflammation or damage to your liver cells. The key liver enzymes measured in a “Liver Function Panel” during routine blood tests typically include:
- Alanine aminotransferase (ALT): This is primarily found in liver cells hence it is considered more specific for the liver. Elevated ALT levels often indicate liver damage or inflammation.
- Aspartate aminotransferase (AST):This is present in the liver but also the heart, pancreas, muscles, and other tissues. Elevated AST levels may suggest liver damage but may also be from others since AST can be found in other tissues in the body hence it is less specific for the liver.
- Alkaline phosphatase (ALP): ALP is found in the liver, bile ducts, and bone. Oftentimes, ALP is coupled with the enzyme Gamma-glutamyl transferase (GGT) to differentiate the source of ALP elevation i.e. whether the ALP elevation is from the liver and bile ducts or the bones.
- Gamma-glutamyl transferase (GGT): Elevated levels can indicate liver or bile duct damage and may be a marker of alcohol use. This enzyme can also be affected by certain medications.
Your symptoms, medical history, and the pattern of these liver function test (LFT) abnormalities often provide your doctor with clues as to the underlying cause of elevated LFTs.
What Is the Most Common Cause of Elevated Liver Function Tests (LFTs) Worldwide and in Singapore?
Globally, the most common cause of elevated LFTs is viral hepatitis, particularly hepatitis B and hepatitis C.
- Hepatitis B is widespread in Asia, Africa, and parts of the Middle East. It is transmitted through blood, sexual contact, and from mother to child during childbirth.
- Hepatitis C is prevalent in many regions, including parts of Eastern Europe, Central Asia, and Egypt. It is primarily spread through blood-to-blood contact, such as via unsterilized medical equipment, blood transfusions, and intravenous drug use.
Chronic infections with hepatitis B and C can lead to liver inflammation, elevated liver function tests, cirrhosis, and liver cancer. In many developing regions, the prevalence of hepatitis B and C is much higher, making these the leading causes of elevated LFTs worldwide.
In Singapore, hepatitis B remains an important cause of liver disease, but vaccination programs have significantly reduced the incidence of new cases. Consequently, the most common reason for elevated LFTs in Singapore is now non-alcoholic fatty liver disease (NAFLD). This condition is increasingly prevalent due to rising rates of obesity, diabetes, and metabolic syndrome, all strongly associated with NAFLD. NAFLD can progress to liver inflammation (non-alcoholic steatohepatitis or NASH), fibrosis, and cirrhosis.
What Are Other Causes of Elevated Liver Function Tests (LFTs)?
Besides hepatitis B, hepatitis C, and NAFLD, other common causes of elevated LFTs include:
- Alcoholic Liver Disease: Excessive alcohol consumption can damage liver cells, leading to conditions like alcoholic hepatitis or cirrhosis. A general guideline for moderate alcohol consumption is up to 2 standard drinks per day for men and 1 standard drink per day for women. However, even at moderate drinking, this can cause elevated liver enzymes in some individuals. Individuals with certain medical conditions (e.g., liver disease), those taking medications that interact with alcohol, pregnant women, and those with a history of alcohol use disorder should avoid alcohol entirely.
- Medications, Supplements, and Alternative Medicine: Many drugs can affect liver function tests, including over-the-counter pain relievers like paracetamol (Panadol), certain antibiotics, statins (used to lower cholesterol), and anticonvulsants. Herbal supplements and recreational drugs can also contribute to liver enzyme elevation. These are factors to consider when you have elevated LFTs.
- Viral Infections: Besides hepatitis B and C, there are many other viral infections that can cause elevated LFTs. Some of these include mononucleosis (Epstein-Barr virus), cytomegalovirus (CMV), dengue, and COVID-19. Many viruses that cause elevated LFTs cannot be identifiable but in many cases will resolve on their own. Some however will require additional treatment.
- Autoimmune hepatitis (AIH): AIH is a chronic liver disease where the body’s immune system attacks liver cells, leading to inflammation and, over time, liver damage. The exact cause of autoimmune hepatitis is not fully understood, but it is frequently associated with female gender and a personal or family history of autoimmune disorders such as diabetes type 1, rheumatoid arthritis, celiac disease, lupus, and autoimmune thyroid disorders.
- Gallbladder or Bile Duct Issues: Conditions such as gallstones, bile duct obstructions, or cholangitis (inflammation of the bile duct) can cause elevated LFTs. Early symptoms may include colicky right upper quadrant abdominal pain after a fatty meal due to transient cystic or bile duct obstruction from gallstones. However, with persistent obstruction this can lead to infections such as acute cholecystitis (inflammation of the gallbladder) or cholangitis which can be life-threatening and require urgent evaluation and treatment.
- Genetic Conditions: Less common causes include genetic conditions like hemochromatosis and Wilson’s disease, which result in the accumulation of iron and copper, respectively, in the liver causing liver inflammation and other organ damage.
Can Elevated Liver Function Tests (LFTs) Be Due to Non-Liver Causes?
Yes, elevated LFTs can sometimes be due to non-liver causes, such as:
- Celiac Disease: An autoimmune disorder where ingestion of gluten leads to small intestine damage. In some cases, this is associated with elevated LFTs though the exact mechanism of how this occurs is not fully understood. The liver function tests often normalize with a strict gluten-free diet.
- Thyroid Disorders: Both hypothyroidism and hyperthyroidism can affect liver enzyme level due to a variety of mechanisms, including metabolic changes, impaired bile flow, or associated autoimmune processes. These liver enzyme abnormalities often help with appropriate treatment of the underlying thyroid condition.
- Muscle Diseases: Conditions like myositis (where the immune system attacks muscles) and rhabdomyolysis (muscle cell breakdown due to trauma or extreme exercise) can cause “elevated LFTs.” However, in these cases, the elevated enzymes (AST and ALT) reflect muscle damage rather than liver damage.
How Will the Doctor Evaluate the Cause of My Elevated Liver Function Tests?
Your doctor will review your medical history and perform a physical examination. They will assess your LFT results to determine if additional tests are needed, such as further blood tests or imaging studies like an ultrasound, CT, or MRI. These tests help to:
- Confirm if there is inflammation in the liver.
- Identify the cause of the inflammation.
- Determine the extent of liver damage.
Based on this information, your doctor will recommend a tailored management plan to prevent further liver damage and manage any underlying conditions.
