The liver plays a central role in various bodily functions, including metabolism, digestion, and detoxification. It utilizes specialized proteins known as liver enzymes. These enzymes are typically contained within liver cells; however, when liver cells are damaged or inflamed, they can leak into the bloodstream. Measuring these levels through blood tests can indicate liver health. COVID-19, the disease caused by the SARS-CoV-2 virus, can indeed lead to elevated liver enzymes.
Liver Enzymes and COVID-19’s Connection
Patients with COVID-19 frequently show elevated levels of specific liver enzymes, particularly alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes indicate hepatocellular injury, or damage to liver cells. While ALT is more specific to the liver, AST can also originate from other organs like the heart and muscles. Doctors often compare ALT and AST levels to determine if the liver is the primary source of the elevation.
The prevalence of elevated liver enzymes in COVID-19 patients varies, with reports indicating ranges from 14% to 76% of patients. A meta-analysis of over 20,000 COVID-19 patients found that approximately 23.1% had elevated liver enzymes upon presentation. The degree of enzyme elevation can correlate with disease severity, with higher levels often seen in patients with more severe COVID-19, including those requiring intensive care or experiencing poorer outcomes.
How COVID-19 Can Elevate Liver Enzymes
Several mechanisms contribute to liver enzyme elevation in individuals with COVID-19. One direct cause is the SARS-CoV-2 virus infecting liver cells. It binds to ACE2 receptors on liver and bile duct cells, leading to direct cellular damage, inflammation, and injury.
The body’s immune response also plays a significant role. A severe inflammatory reaction, often called a “cytokine storm,” can lead to widespread inflammation affecting multiple organs, including the liver, resulting in liver cell injury.
Medications used to treat COVID-19 can also induce liver stress. Drug-induced liver injury (DILI) has been observed in up to 25.4% of COVID-19 patients. Antivirals like remdesivir and lopinavir/ritonavir, as well as certain anti-inflammatory drugs, have been associated with elevated liver enzymes.
COVID-19 can worsen liver function in individuals with pre-existing liver conditions. Patients with underlying chronic liver diseases, such as fatty liver disease or cirrhosis, may experience more severe liver injury due to their reduced liver reserve. In severe COVID-19 cases, reduced oxygen supply to the liver (hypoxia) due to respiratory complications can also lead to liver cell damage.
What Elevated Liver Enzymes Mean After COVID-19
Elevated liver enzymes following a COVID-19 infection often follow a mild and transient course. In most instances, these enzyme levels return to normal as the body recovers from the viral illness. Many individuals with elevated liver enzymes due to COVID-19 may not experience noticeable symptoms.
However, in some cases, symptoms such as fatigue, nausea, or, less commonly, jaundice (yellowing of the skin or eyes) can occur, particularly with more significant liver involvement. Persistent elevations or the development of new symptoms warrant follow-up with a healthcare provider. Monitoring liver function tests is important, especially for those with pre-existing liver conditions or who experienced severe COVID-19.
While severe liver injury or acute liver failure due to COVID-19 is rare, elevated liver enzymes, especially AST, have been linked to increased disease severity and poorer outcomes during hospitalization. For most patients, liver function normalizes as they recover, but ongoing or significantly high enzyme levels might indicate a need for further investigation to rule out other causes or assess any potential long-term effects on liver health.