What is the significance of AST (aspartate aminotransferase) at 11 and ALT (alanine aminotransferase) at 6 in a 22-year-old female's liver function test results?

Unusually Low Transaminase Levels in a Young Female

These AST and ALT values (11 and 6 U/L respectively) are significantly below the normal reference range for a 22-year-old female and warrant clinical correlation, though they do not indicate liver disease.

Understanding Normal Reference Ranges

• Normal ALT levels for women are 19-25 IU/L, making this patient's ALT of 6 U/L markedly below the lower limit of normal 1
• Normal AST levels are similarly in the range of 19-33 IU/L for women, making the AST of 11 U/L also below normal 1
• Both values are approximately 30-50% of the lower limit of normal, which is an unusual finding 2

Clinical Significance of Low Transaminases

Low transaminase levels do not indicate liver dysfunction or disease. The clinical concern with liver enzymes relates to elevations, not reductions 2, 1. However, unusually low values warrant consideration of:

Potential Explanations

• Nutritional deficiencies: Vitamin B6 (pyridoxine) deficiency can result in low ALT and AST levels, as these enzymes require pyridoxal-5-phosphate as a cofactor 3
• Low muscle mass or sarcopenia: Since AST is present in skeletal muscle, very low muscle mass can contribute to low baseline levels 4
• Chronic kidney disease: Advanced renal disease can be associated with lower transaminase levels 4
• Laboratory variation: Consider repeat testing to confirm these values are consistently low and not a laboratory error 2

Recommended Clinical Approach

Immediate Assessment

• Obtain a detailed nutritional history, including dietary patterns, weight changes, and any restrictive eating behaviors 1
• Assess for signs of malnutrition or vitamin deficiencies, including neurologic symptoms that might suggest B6 deficiency 3
• Evaluate muscle mass and overall body composition, particularly in the context of the patient's BMI and physical activity level 4
• Review the complete metabolic panel for other abnormalities that might provide context, such as low albumin or abnormal creatinine 2

Follow-up Testing

• Repeat liver function tests in 2-4 weeks to confirm these values are persistent rather than a one-time laboratory anomaly 1
• Consider vitamin B6 levels if nutritional deficiency is suspected based on history 3
• No urgent intervention is required unless other clinical findings suggest underlying pathology 2, 1

Important Clinical Caveats

• This pattern does NOT indicate liver disease or dysfunction—liver disease manifests with elevated, not decreased, transaminases 2, 1
• Preserved synthetic function (normal albumin, bilirubin, and coagulation studies) confirms the liver is functioning normally despite the low enzyme levels 1
• The AST/ALT ratio of 1.83 is not clinically meaningful in the context of both values being below normal range; this ratio is only interpretable when values are elevated 2, 5
• Gender-specific reference ranges matter: Women naturally have lower transaminase levels than men, but these values are still below the female reference range 6

When to Refer

• Hepatology referral is NOT indicated for isolated low transaminase levels in the absence of other liver abnormalities 1
• Consider nutrition consultation if dietary deficiency or eating disorder is suspected based on clinical assessment 3
• Routine monitoring is appropriate if no concerning features are identified on history and physical examination 1