Elevated transaminases (ALT and AST)

What ALT and AST are

ALT (alanine aminotransferase, also called SGPT) and AST (aspartate aminotransferase, SGOT) are enzymes found inside cells. Only small amounts are present in the blood. When cells are damaged or die, the enzymes leak into the blood and their values rise. They are therefore markers of cell injury, not measures of liver function.

ALT is found mainly in the liver, so its rise is more closely tied to a liver problem. AST is also found in muscle (including heart muscle), kidney, brain and blood cells, so its rise does not always come from the liver. A rise in AST after hard physical effort, after a muscle injury or with muscle disease can be explained without any liver problem.

Reference values vary from laboratory to laboratory (depending on the method, age and sex). For this reason, always read your result against the range printed on your report and not against a general number.

To judge actual liver function, other markers are reviewed: bilirubin, albumin and INR (clotting time), which show whether the liver is managing to do its work, as well as the bile duct enzymes (ALP, GGT).

Why they can rise

The causes are many; the most common are:

• hepatic steatosis (fatty liver), linked to overweight, diabetes, high cholesterol and the metabolic syndrome. It is the most common cause of a mild rise in ALT;
• alcohol-related injury, even when the amount drunk does not seem large to the patient;
• viral hepatitis: B, C, more rarely A and E;
• medicines, herbal products and supplements: acetaminophen in high doses, some antibiotics, statins (rarely), anti-inflammatory drugs, anti-seizure medicines, and “natural” or “detox” products;
• autoimmune disease (autoimmune hepatitis) and metabolic or inherited disease (hemochromatosis, Wilson disease, alpha-1 antitrypsin deficiency);
• celiac disease, thyroid disease and other systemic conditions that can mildly raise the enzymes;
• muscle injury, including very strenuous exercise, trauma and some myopathies;
• heart and circulation problems: congestion of the liver in heart failure, or severe hypoperfusion.

The AST/ALT ratio can give a clue (for example, AST higher than ALT is seen more often in alcohol-related disease), but the cause is not determined by this ratio alone.

Does the value show how damaged the liver is

Not necessarily. The level of transaminases shows more how active the cell injury is right now, not how damaged the liver is overall. A person with advanced cirrhosis may have low or normal ALT, while a person with acute hepatitis may have very high values and recover completely.

• A mild rise (less than about two to three times the upper limit) is common and usually linked to steatosis or medicines, but should not be neglected if it persists.
• A marked rise (many times the upper limit) needs faster evaluation, because it may indicate acute viral hepatitis, drug-induced injury or poisoning, bile duct obstruction or a severe circulation problem.
• A single elevated result does not prove serious disease. On the other hand, normal values do not exclude every chronic liver disease.

How the evaluation is done

The evaluation follows a logical order and is often not rushed:

1. History: symptoms, duration, alcohol (the exact amount), all medicines, supplements, teas and herbal products you use, travel, procedures or exposures to blood, family history of liver disease, weight and its changes.
2. Repeating or completing the tests: the first step is often to repeat ALT/AST together with bilirubin, albumin, INR, ALP and GGT, as well as a blood count (platelets).
3. Looking for the cause, as appropriate: hepatitis B and C markers, glucose and lipid profile, iron and ferritin, tests for celiac disease and thyroid, CK (to exclude a muscle origin) and selected tests for autoimmune or metabolic disease.
4. Abdominal ultrasound: shows steatosis, the shape of the liver, the gallbladder and bile ducts, the spleen and signs of portal hypertension.
5. Assessment of fibrosis when indicated (in steatosis, alcohol-related disease, chronic hepatitis): with indexes from blood tests such as FIB-4 and, if needed, with elastography. Fibrosis is what determines the outlook most.

The timing of follow-up depends on the level of elevation and the clinical situation. Not every result should simply be repeated after a few months, and not every mild rise needs extensive tests: the doctor chooses according to the patient’s risk.

What to do and what to avoid

• Do not use “detox” products or supplements “for the liver” without medical advice; some of them can themselves harm the liver.
• Do not stop prescribed medicines on your own, especially for the heart, diabetes or epilepsy. If you suspect a medicine is the cause, talk to the doctor who prescribed it.
• Limit or avoid alcohol until the cause is clarified.
• Do not exceed the dose of acetaminophen; check that combination cold and flu medicines do not contain it, so you do not take it twice.
• When the cause is steatosis, the key is gradual weight loss, a suitable diet (Mediterranean pattern), regular physical activity and control of diabetes and cholesterol.
• Bring your previous test results and the full list of medicines, teas and herbal products to the visit.