Elevated transaminases
Encyclopedia
In medicine
, the presence of elevated transaminases, commonly the transaminases alanine transaminase
(ALT) and aspartate transaminase
(AST), may be an indicator of liver damage. Other terms employed include transaminasemia and transaminitis, although the latter is considered pathologically meaningless.
, has a variety of transaminase
s to synthesize and break down amino acids and to interconvert energy storage molecules. The concentrations of these in the serum
(the non-cellular portion of blood) are normally low. However, if the liver is damaged, the hepatocyte
cell membrane
becomes more permeable and some of the enzymes leak out into the blood stream. The two transaminases commonly measured are alanine transaminase
(ALT) and aspartate transaminase
(AST). These levels previously were called the serum glutamate-pyruvate transaminase (SGPT) and the serum glutamate-oxaloacetate transaminase (SGOT). Elevated levels are quite sensitive for liver injury, meaning that they are likely to be present if there is injury. However, they may also be elevated in other conditions. ALT is not commonly found outside the liver; AST too is most commonly found in the liver, but also in significant amounts in cardiac
(heart) and skeletal muscle
. In fact, measurement of these used to be part of diagnosing heart attack
s, although newer enzymes and proteins that are more specific for cardiac damage have largely replaced this usage.
, liver injury from lack of blood flow, or injury from drugs or toxins. Most disease processes cause ALT to rise higher than AST; AST levels double or triple that of ALT are consistent with alcoholic liver disease
.
Levels over 1000 can be associated with ischemic hepatitis
.
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, the presence of elevated transaminases, commonly the transaminases alanine transaminase
Alanine transaminase
Alanine transaminase or ALT is a transaminase enzyme . It is also called serum glutamic pyruvic transaminase or alanine aminotransferase ....
(ALT) and aspartate transaminase
Aspartate transaminase
Aspartate transaminase , also called aspartate aminotransferase or serum glutamic oxaloacetic transaminase , is a pyridoxal phosphate -dependent transaminase enzyme . AST catalyzes the reversible transfer of an α-amino group between aspartate and glutamate and, as such, is an important enzyme in...
(AST), may be an indicator of liver damage. Other terms employed include transaminasemia and transaminitis, although the latter is considered pathologically meaningless.
Pathophysiology
The biochemical hub of the body, the liverLiver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, has a variety of transaminase
Transaminase
In biochemistry, a transaminase or an aminotransferase is an enzyme that catalyzes a type of reaction between an amino acid and an α-keto acid. To be specific, this reaction involves removing the amino group from the amino acid, leaving behind an α-keto acid, and transferring it to the...
s to synthesize and break down amino acids and to interconvert energy storage molecules. The concentrations of these in the serum
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
(the non-cellular portion of blood) are normally low. However, if the liver is damaged, the hepatocyte
Hepatocyte
A hepatocyte is a cell of the main tissue of the liver. Hepatocytes make up 70-80% of the liver's cytoplasmic mass.These cells are involved in:* Protein synthesis* Protein storage* Transformation of carbohydrates...
cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
becomes more permeable and some of the enzymes leak out into the blood stream. The two transaminases commonly measured are alanine transaminase
Alanine transaminase
Alanine transaminase or ALT is a transaminase enzyme . It is also called serum glutamic pyruvic transaminase or alanine aminotransferase ....
(ALT) and aspartate transaminase
Aspartate transaminase
Aspartate transaminase , also called aspartate aminotransferase or serum glutamic oxaloacetic transaminase , is a pyridoxal phosphate -dependent transaminase enzyme . AST catalyzes the reversible transfer of an α-amino group between aspartate and glutamate and, as such, is an important enzyme in...
(AST). These levels previously were called the serum glutamate-pyruvate transaminase (SGPT) and the serum glutamate-oxaloacetate transaminase (SGOT). Elevated levels are quite sensitive for liver injury, meaning that they are likely to be present if there is injury. However, they may also be elevated in other conditions. ALT is not commonly found outside the liver; AST too is most commonly found in the liver, but also in significant amounts in cardiac
Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...
(heart) and skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
. In fact, measurement of these used to be part of diagnosing heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
s, although newer enzymes and proteins that are more specific for cardiac damage have largely replaced this usage.
Role in diagnosis
In general, any damage to the liver will cause medium elevations in these transaminases (usually called liver enzymes, though of course they are not the only enzymes in the liver). And diagnosis requires synthesis of many pieces of information, including the patient's history, physical examination, and possibly imaging or other laboratory examinations. However, very high elevations of the transaminases suggests severe liver damage, such as viral hepatitisViral hepatitis
Viral hepatitis is liver inflammation due to a viral infection. It may present in acute or chronic forms. The most common causes of viral hepatitis are the five unrelated hepatotropic viruses Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, and Hepatitis E...
, liver injury from lack of blood flow, or injury from drugs or toxins. Most disease processes cause ALT to rise higher than AST; AST levels double or triple that of ALT are consistent with alcoholic liver disease
Alcoholic liver disease
Alcoholic liver disease is a term that encompasses the hepatic manifestations of alcohol overconsumption, including fatty liver, alcoholic hepatitis, and chronic hepatitis with hepatic fibrosis or cirrhosis. It is the major cause of liver disease in Western countries...
.
Levels over 1000 can be associated with ischemic hepatitis
Ischemic hepatitis
Ischemic hepatitis is a condition of decreased blood supply to the liver resulting in injury to liver cells , which occurs in a diffuse fashion. The decreased blood flow to the liver is usually due to shock or low blood pressure...
.