Alanine Aminotransferase (ALT) is an enzyme primarily found in the liver, with smaller amounts in the kidneys, heart, and muscles. It plays a vital role in breaking down proteins and converting them into energy. ALT is released into the bloodstream when the liver is damaged or inflamed. Clinically, ALT is a key biomarker for liver health, as elevated levels often indicate liver injury or disease. Understanding ALT levels helps clinicians diagnose liver disorders, monitor disease progression, and guide treatment decisions.
ALT measurements are useful in diagnosing and managing liver diseases such as viral hepatitis and cirrhosis. ALT activity is generally lower than aspartate aminotransferase (AST) activity and is highest in the liver. Significant ALT elevations occur mainly in liver diseases. ALT is often measured with AST to determine if AST's source is the liver or heart. A normal ALT with elevated AST suggests cardiac disease, while slight ALT elevations can occur with extensive heart muscle damage.
Abnormal ALT Levels
Low ALT: Low ALT levels can result from chronic liver disease, malnutrition, advanced liver cirrhosis, severe vitamin B6 deficiency, or genetic disorders affecting ALT production. Although low ALT levels are less common, they can indicate significant liver damage and require further evaluation.
Symptoms of Low ALT Levels are less common and generally less concerning but can include:
- Muscle weakness
- Fatigue
- Generalized symptoms: Symptoms related to the underlying condition causing low ALT levels.
High ALT: High ALT levels typically signal liver damage or injury, either acute or chronic. Common causes include hepatitis, fatty liver disease, and cirrhosis. Other causes include certain medications (statins, antibiotics, and OTC pain relievers), excessive alcohol consumption, obesity, metabolic disorders like diabetes, and toxin exposure.
ALT levels may also rise temporarily after strenuous exercise or muscle injury, though elevations are more specific to liver injury.
Identifying the cause of elevated ALT is crucial for proper management and treatment, including ruling out drug, alcohol, medication use, and toxin exposure.
Symptoms of Elevated ALT Levels often indicate liver damage or inflammation and can include:
- Fatigue: Persistent tiredness and lack of energy
- Abdominal discomfort or pain: Especially in the upper right side of the abdomen.
- Jaundice: Yellowing of the skin and eyes, indicating bilirubin buildup.
- Dark urine: Darker than usual due to bilirubin in the urine.
- Pale stools: Stools may be lighter in color, indicating issues with bile production.
- Nausea and vomiting: Feeling sick to the stomach or vomiting.
- Loss of appetite: Decreased desire to eat, sometimes leading to weight loss.
- Swelling: Swelling in the abdomen or legs due to fluid buildup (ascites or edema).
- Itchy skin: Generalized itching without an apparent cause.
- Bruising or bleeding: Increased tendency to bruise or bleed easily.
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