SGOT and SGPT are older names for two enzymes commonly measured in the blood to assess liver health: Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT). These enzymes are typically included in a standard blood test panel, often referred to as a Liver Function Test (LFT) or liver chemistry panel. Measuring the levels of these aminotransferases provides an important initial indicator of potential damage or inflammation within the liver. The modern nomenclature, AST and ALT, has largely replaced the older terms, Serum Glutamic Oxaloacetic Transaminase (SGOT) and Serum Glutamic Pyruvic Transaminase (SGPT), respectively.
The Normal Roles of AST and ALT
AST and ALT play a part in the body’s metabolism of amino acids, the building blocks of proteins. Their primary function involves a transfer reaction, moving an amino group from an amino acid to a keto-acid. This process is necessary for energy production and the synthesis of other molecules within cells.
Alanine Aminotransferase (ALT) is highly concentrated within liver cells, making it a more specific indicator of liver health. Aspartate Aminotransferase (AST) is also found in the liver, but it is distributed more widely throughout the body. Significant amounts of AST are present in the heart, skeletal muscles, kidneys, and brain. This broader distribution means that elevated AST can sometimes result from damage in organs other than the liver.
What Elevated Levels Indicate
Elevated levels of AST and ALT in the bloodstream result directly from cellular injury. When cells, particularly liver cells (hepatocytes), are damaged or die due to inflammation or disease, their membranes become permeable, releasing these enzymes into the circulation. The measurement of these enzymes is therefore a sensitive way to detect injury to the liver or other enzyme-containing tissues.
The degree of elevation offers clues regarding the severity of the injury. Levels more than ten times the upper limit of normal often suggest acute hepatitis or severe toxic injury, such as an acetaminophen overdose. Mild elevations, typically less than five times the upper limit, are common in routine blood work and may be caused by various conditions. The enzyme level itself indicates the degree of ongoing cell injury, not necessarily the extent of liver function loss.
Primary Causes of High AST and ALT Readings
Liver-Related Causes
The most frequent cause of mild to moderate elevation in AST and ALT is Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), formerly known as Non-Alcoholic Fatty Liver Disease (NAFLD). This condition is strongly linked to obesity, type 2 diabetes, and high cholesterol, affecting a large percentage of the population. Fatty liver disease causes chronic inflammation and damage to the hepatocytes, leading to a persistent release of the enzymes.
Alcohol-related liver disease is another common cause, often presenting a distinct pattern where the AST level is typically at least twice as high as the ALT level (AST/ALT ratio \(\geq 2\)). This specific ratio occurs because alcohol depletes a cofactor required for ALT synthesis and damages mitochondria, which contain AST.
Toxic or drug-induced liver injury is also a significant factor. Culprits include common over-the-counter pain relievers, such as acetaminophen, and certain prescription medications, including statins. Even some herbal supplements and high-dose vitamins can cause liver stress and elevated readings. Viral hepatitis, specifically chronic Hepatitis B and C, also causes ongoing liver cell destruction and frequent enzyme elevation.
Non-Hepatic Causes
Non-hepatic causes must be considered, particularly when the AST is disproportionately higher than the ALT, or when both are mildly elevated. These conditions cause AST and sometimes ALT to rise due to their presence in other tissues:
- Severe muscle injury from intense exercise.
- Muscle diseases like polymyositis.
- Celiac disease.
- Thyroid disorders.
- A recent heart attack or severe tissue damage (rhabdomyolysis), which causes a sharp, temporary spike in AST.
Diagnostic Steps and Management
When a blood test reveals elevated AST and ALT levels, a comprehensive assessment is required to pinpoint the underlying cause of the cellular damage. Healthcare providers often order additional blood work, including tests for Alkaline Phosphatase (ALP) and Gamma-Glutamyl Transferase (GGT), to confirm if the liver is the primary source. The ratio of AST to ALT, sometimes called the Ritis Ratio, helps differentiate conditions, as a ratio greater than 2 strongly suggests alcohol-related damage.
Targeted testing may include viral hepatitis panels, iron studies to check for hemochromatosis, and lipid profiles to assess for metabolic syndrome. Abdominal imaging, such as an ultrasound, is frequently used to visualize the liver for signs of fatty infiltration, scarring (cirrhosis), or bile duct blockage. Management begins with lifestyle changes, such as modifying diet, achieving modest weight loss if overweight, and strictly avoiding alcohol and potential hepatotoxic medications. If enzyme levels remain significantly elevated after observation, a referral to a specialist for further evaluation, potentially including a liver biopsy, is necessary.