From the Guidelines
Elevated aspartate aminotransferase (AST) in a patient taking Armour Thyroid (Desiccated Thyroid) is likely indicative of non-hepatic causes, such as thyroid disease, given the patient's medication regimen.
Possible Causes of Elevated AST
- Thyroid disease: Elevated AST levels can be associated with thyroid disorders, including those treated with desiccated thyroid 1.
- Hepatocellular injury: Although less likely in this context, hepatocellular injury due to various causes, including fatty liver disease, viral hepatitis, and drug-induced liver injury, can also lead to elevated AST levels 1.
- Other non-hepatic causes: Other potential causes of elevated AST include hemolysis, myopathy, and exercise 1.
Clinical Considerations
In patients with elevated AST, it is essential to consider the AST:ALT ratio, which can help differentiate between hepatic and non-hepatic causes 1. A ratio of >2 is often seen in alcohol-induced liver disease, while a ratio of <1 is more commonly associated with metabolic disease-related fatty liver.
Diagnostic Approach
When evaluating a patient with elevated AST, a comprehensive diagnostic approach should include laboratory tests, such as ALT, ALP, and bilirubin, as well as imaging studies to assess liver morphology and rule out other potential causes 1.
From the Research
Significance of Elevated Aspartate Aminotransferase (AST) in a Patient Taking Armour Thyroid (Desiccated Thyroid)
- Elevated AST levels can be associated with various conditions, including liver diseases and thyroid disorders 2.
- In patients taking Armour Thyroid (Desiccated Thyroid), elevated AST levels may not necessarily indicate liver damage, as thyroid hormones can affect liver function and bilirubin metabolism 2.
- A rare and benign cause of isolated AST increase is the presence of macro-aspartate aminotransferase (macro-AST), which can lead to diagnostic confusion in patients with chronic liver disease or other conditions 3, 4, 5, 6.
- Macro-AST is a high-molecular mass complex that can cause isolated elevation of serum AST activity, and its presence can be confirmed using methods such as polyethylene glycol precipitation or ultracentrifugation 4, 5, 6.
- Clinicians should consider testing for macro-AST when elevated AST is the only abnormal lab finding, as this condition is benign and does not require specific treatment 5, 6.
Possible Causes of Elevated AST in Patients Taking Armour Thyroid
- Thyroid diseases, such as hypothyroidism, can be associated with elevated AST levels 2.
- Liver diseases, such as hepatitis C virus infection, can also be associated with thyroid test abnormalities or dysfunctions 2.
- Macro-AST can be present in asymptomatic patients, including those taking Armour Thyroid, and can cause isolated elevation of AST levels 4, 6.
Clinical Implications
- Clinicians should be aware of the possible causes of elevated AST levels in patients taking Armour Thyroid, including thyroid diseases, liver diseases, and macro-AST 2, 3, 4, 5, 6.
- Testing for macro-AST should be considered when elevated AST is the only abnormal lab finding, to avoid unnecessary investigations and patient anxiety 5, 6.