Liver Enzymes Elevated in Starvation and Extreme Fasting
During starvation or extreme fasting, ALT (alanine transaminase) and AST (aspartate transaminase) are the primary liver enzymes that become elevated, with ALT being the most specific marker for hepatocellular injury in this context. 1
Pattern of Enzyme Elevation
ALT is the most liver-specific enzyme and rises during starvation because it is primarily concentrated in liver tissue with minimal presence in cardiac muscle, skeletal muscle, or red blood cells 2, 3
AST also elevates during starvation but is less specific for liver injury since it exists in cardiac muscle, skeletal muscle, kidneys, brain, and red blood cells 2, 4
The elevation typically occurs as a hepatocellular injury pattern rather than a cholestatic pattern, meaning ALT and AST rise while alkaline phosphatase remains relatively normal 2
Clinical Course and Mechanism
Starvation-induced liver enzyme elevation follows a characteristic pattern: enzymes may paradoxically worsen after refeeding is initiated, with body weight inversely associated with liver enzyme levels during the early refeeding period 1
This represents a different course from refeeding syndrome, where the clinical picture includes electrolyte disturbances and other metabolic derangements 1
Normalization of liver enzymes occurs as caloric intake increases and weight gain progresses, distinguishing this from other causes of transaminase elevation 1
Severity and Monitoring
Starvation typically causes mild to moderate elevations (less than 5 times the upper limit of normal), though the exact degree varies with the severity and duration of malnutrition 5
Daily changes in body weight serve as a useful clinical marker for distinguishing between refeeding syndrome and starvation-induced liver enzyme elevation 1
The AST/ALT ratio typically remains less than 1 in starvation-induced hepatocellular injury, similar to other non-alcoholic causes of liver injury 2
Important Clinical Caveats
Do not confuse starvation-induced enzyme elevation with refeeding syndrome: in starvation-induced elevation, enzymes may worsen initially after feeding begins but then normalize with continued adequate nutrition, whereas refeeding syndrome presents with electrolyte abnormalities and potentially life-threatening complications 1
Synthetic liver function remains preserved during starvation-induced enzyme elevation, meaning albumin, bilirubin, and prothrombin time/INR remain normal despite transaminase elevations 2
The elevation resolves with adequate nutritional repletion, making this a reversible condition that does not require specific hepatotoxic drug therapy 1
If transaminases remain elevated despite adequate refeeding and weight gain over 4-6 weeks, alternative diagnoses such as non-alcoholic fatty liver disease, medication-induced liver injury, or viral hepatitis must be considered 2, 5