GPT (Alanineaminotransferase)

Norm
Women 5–35 U/l
Men 10–40 U/l
Children
up to 1 year 15–54 U/l
1–6 years 5–35 U/l
7–17 years 10–24 U/l

Synonyms: alanine aminotransferase, ALT, ALAT, serum glutamate pyruvate transaminase, 2-oxoglutarate aminotransferase.
Serum, plasma heparin
Cap red or green

Elevated GPT (alanine aminotransferase) enzyme activity is most commonly assessed as an indicator of liver pathology. GPT (ALT, alanine aminotransferase) is one of the two transaminases used in clinical practice. GPT (ALT) is found in almost all tissue cells. The highest GPT (ALT) activity is detected in the liver, kidneys, muscles, and leukocytes. GPT (ALT) is almost exclusively localized in the cell cytoplasm. It is not found in mitochondria. GPT (ALT) is one of the most sensitive indicators of liver damage. In the case of liver damage, GPT (ALT) activity in the serum rapidly increases. In the case of kidney, heart muscle, skeletal muscle, and hematopoietic organ damage, there are no significant changes in this enzyme.

The most significant changes in GPT (ALT) activity (increase by ten times or more) are detected in acute hepatitis. GPT (ALT) activity begins to increase at the end of the incubation period (5–6 days before the onset of jaundice). When the patient turns yellow, there is usually a peak in GPT (ALT) activity. The significantly increased enzyme activity persists for another 5–6 days, and the indicator may return to normal levels within 6–7 weeks. Prolonged elevation of GPT (ALT) indicates an unfavorable prognosis for liver disease. GPT (ALT) activity also increases in cases of non-jaundiced hepatitis. During acute hepatitis, the concentration of bilirubin increases approximately 1 week later than the increase in GPT (ALT). The concentration of bilirubin in the serum also returns to normal levels faster than GPT (ALT) (this is called “phase crossover”). The enzyme is less affected in drug-induced, toxic, mechanical hepatitis, cholecystitis, and hepatic coma. However, GPT (ALT) activity will be high if hepatic coma develops against the background of acute hepatitis. During myocardial infarction, GPT (ALT) increases only if the necrosis involves a large area of the heart muscle.

The increase in enzyme activity correlates well with the severity of the liver process. An increase in GPT indicates hepatocyte damage better than mechanical liver and biliary tract obstruction. GPT elevation is most commonly relied upon to identify a slow-progressing liver disease, diagnose hepatitis, cirrhosis. GPT is used to assess the activity of chronic hepatitis C. In alcoholic liver disease, GPT is a slightly less specific indicator than AST. GPT activity sometimes increases in cases of obesity. Liver enzymes GPT and AST are usually determined together. Clinical evaluation is based on their ratio calculation (De Ritis coefficient). The De Ritis ratio GOT/GPT (or alternatively AST/ALT ratio) is normally 1.3 ± 0.4. An increase in this ratio makes heart damage (myocardial infarction) more likely, and conversely, a decrease indicates liver pathology. Based on the values of this ratio, an approximate initial differentiation of liver diseases is possible (see the table). For more information, see “Liver Laboratory Indicators”.

Source | Handbook of Basic Laboratory Tests | Doctor of Medical Sciences Gintaras Zaleskis