By David E. Johnson, M.D.
Fatty liver (steatosis of the liver) is one of the most common reasons people have abnormal liver blood tests. The liver is very active in handling fat. It takes lipoproteins (fats) from the blood, reworks them, and secretes them in a different form. The liver also makes and burns fat. When the balance among these activities changes, fat droplets can accumulate in the liver.
Most often fatty liver occurs in persons with obesity or type 2 (adult-onset) diabetes. Some medications can cause fatty liver. The most important factor in fatty liver is insulin resistance. The body’s sensitivity to insulin can go down with increasing body weight, age, or related to a family history of type 2 diabetes. People with increased fat around the abdomen are more likely to have insulin resistance than people with fat elsewhere. With decreased sensitivity to insulin the body must make more insulin to regulate blood sugar. High blood insulin levels cause increased blood pressure, increased triglycerides, and fatty liver. Excessive alcohol intake also causes fatty liver because of the way alcohol is burned in the liver.
Most persons with fatty liver have no symptoms. If the liver is enlarged a lot there may be an ache or mild tenderness in the right upper abdomen. The GOT or GPT (also known as AST and ALT) liver blood tests are often slightly elevated, usually less than twice normal. Ultrasound of the abdomen usually shows the liver is “echogenic,” that is more dense than usual toward sound waves. The liver can also be enlarged due to fat. Ultrasound does not really measure fat, but the great majority of the time an echogenic liver is found, this is related to excess fat. Excess liver fat can also be detected by CT scan.
At least 80% of persons with fatty liver do not develop any serious problems. If they lose weight and reduce their alcohol intake the fat goes away and the liver returns to normal. Some 10 to 20% of persons with fatty liver can develop a more serious form of fatty liver (steatohepatitis, termed non-alcoholic steatohepatitis or NASH) in which fat causes inflammation and fibrosis (scar tissue) in the liver. Occasionally this form of fatty liver can lead to cirrhosis and liver failure.
We commonly become aware of an issue with the liver because of an abnormality on ultrasound or because of elevated levels of GOT or GPT in blood. GOT and GPT are proteins or enzymes found mainly in liver cells. When they are elevated in the blood it makes us think that some type of inflammation or damage is causing the enzymes to leak out of liver cells. Fatty liver is the most common cause for this. A number of other disorders can cause chronic elevation of GOT and GPT: viral hepatitis B or C, inherited liver disorders (especially iron overload and copper storage disease), autoimmune hepatitis, wheat sensitivity (celiac disease), medications or alcohol, heart failure, and sometimes muscle injury.
Blood tests are usually done for autoimmune, viral, and inherited liver disorders and celiac disease. Blood counts and a prothrombin time blood clotting test are usually done. The history and physical exam may point to a cause for elevated liver enzymes. If nothing is found, and if there are risk factors for fatty liver such as obesity or type 2 diabetes, then fatty liver is likely to be present. The presence of elevated blood triglycerides or low HDL cholesterol suggests insulin resistance, and makes fatty liver likely.
A liver biopsy is often done in persons with unexplained elevated liver tests for more than 6 months. A needle is put quickly in and out of the liver to get a small sample, like a pencil lead about 1 inch long. This is done with some local anesthetic. There may be no pain, or shots of pain medicine may be required. Pain is usually similar to having a dental procedure with local anesthetic. The major risk is bleeding. Bleeding requiring transfusion occurs once in 1,000 biopsies, so it is not common. Patients usually stay a few hours after the biopsy to be sure they feel well.
Many people have fatty liver with mildly elevated liver enzymes, and most of these persons do not have anything seriously wrong with their livers. If the liver enzyme abnormality is mild, such as a GPT up to 1½ times normal, and if nothing turns up on blood tests for autoimmune, viral, and inherited liver disorders, then many experts feel a liver biopsy is not always necessary. If there is a significantly higher GPT level for more than 6 months, then a liver biopsy would be indicated.
For a person with mild enzyme abnormalities and probable fatty liver, a liver biopsy is still the only way to know whether a person has the common, harmless form of fatty liver, or the more serious form. In fact, a person can even have cirrhosis with normal liver enzymes. Persons with more serious fatty liver are usually older, have more extreme obesity, or have type 2 diabetes. However, the only effective treatment for fatty liver is weight loss and exercise to improve insulin resistance. Currently the liver biopsy does not change the treatment. Weight loss usually causes the liver enzymes to normalize. Therefore many people wonder about the need to do a liver biopsy in such persons.
Alcohol intake should be severely restricted. Persons who are overweight should lose weight. Exercise is probably beneficial in combination with weight loss. Weight loss usually causes elevated liver enzymes to go down. The type of diet used to cause weight loss is probably not important as long as weight loss occurs. In fact, fatty liver can be induced by a high-carbohydrate diet, which causes high insulin levels.
Antioxidant agents such as vitamin E or milk thistle have not proven beneficial. Medications used in type 2 diabetes such as metformin or pioglitazone are promising but are not yet used routinely in persons without diabetes.
Persons with more severe changes on liver biopsy are more likely to develop serious liver damage in future years. Relatively few persons with fatty liver develop cirrhosis, except for very obese persons. Most of the time liver damage in fatty liver is a slow process. Liver biopsies done a few years apart usually show little change.