Nonalcoholic steatohepatitis (NASH)

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was reviewed on February 1, 2022.

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD). NASH results from fat buildup—not associated with alcohol use, as the name indicates—and causes the liver to become inflamed and damaged, though it seems to progress slowly.

While as many as 20 percent to 30 percent of people in the United States have NAFLD, according to the U.S. Veterans Health Administration, NASH is less common, with an estimated 2 percent to 5 percent of Americans affected.

Some people with NASH have more severe cirrhosis, which can lead to liver cancer. Cirrhosis occurs when the liver is scarred, causing permanent damage. However, NASH patients who don’t have cirrhosis may also develop primary liver cancer.

NASH symptoms

You can have NASH with no or very few symptoms. You may not even have symptoms if NASH triggers cirrhosis.

Symptoms, if any, may include:

  • Tiredness
  • Discomfort in liver area of the abdomen

In rare cases, children develop NASH, with symptoms such as vomiting and tenderness in their abdomen.

Causes of NASH

Overconsumption of certain nutrients—including iron, cholesterol and refined sugars in processed foods—may raise the chances of developing NAFLD. But doctors don’t know why some people with NAFLD develop NASH and cirrhosis.

NASH is more likely in people with:

  • Large waist
  • High blood pressure
  • High blood sugar or type 2 diabetes
  • High levels of triglycerides in their blood
  • Low levels of good cholesterol (HDL) in their blood
  • Poor diet

Researchers are studying different microorganisms in the intestines and how the body absorbs nutrients for possible causes. Other areas of research on the causes of NASH include:

  • Immune system response to excess fat in the liver
  • Liver or fat cells releasing toxic chemicals called cytokines
  • Liver cells destroying themselves
  • Unstable molecules known as free radicals

Some less common conditions that can contribute to the development of NASH, according to the American Liver Foundation, include:

  • Rapid weight loss
  • Hepatitis C
  • Improper storage of fat as a result of a medical condition
  • Exposure to certain toxins
  • Polycystic ovarian syndrome (PCOS), which affects female hormones
  • Certain medications, such as Cordarone® and Pacerone® (amiodarone), glucocorticoids, Rheumatrex® and Trexall® (methotrexate), synthetic estrogens, Nolvadex® and Soltamox® (tamoxifen)

Risk factors for NASH

People who inherit a variation in the PNPLA3 gene, which provides instructions for making a protein found in fat and liver cells, may be more susceptible to NASH. Researchers are studying this and other genetic changes that may contribute to people developing NASH and its complications.

Although children can develop NASH, people are at greater risk as they age. NASH is also seen at higher rates among those of Hispanic or Asian descent.

How NASH is diagnosed

A NASH diagnosis involves multiple steps, including a physical examination, blood tests, imaging tests, and possibly a liver biopsy.

Medical history and physical exam

Your doctor will start with your medical history to determine whether you have any conditions that can lead to NAFLD and NASH. These include:

  • Being overweight or obese
  • Having type 2 diabetes or insulin resistance
  • Having high levels of triglycerides or cholesterol
  • Having metabolic or insulin resistance syndrome

Your doctor will give you a physical exam to feel if your liver is enlarged and to look for signs of insulin resistance such as darkened skin patches on your knuckles, elbows and knees.

Your doctor will look for signs of cirrhosis, which include:

  • Enlarged spleen
  • Fluid in your abdomen
  • Muscle loss

Blood tests

You will likely undergo blood tests to look for high levels of liver enzymes such as:

  • Alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)

Other blood tests can show whether you have liver fibrosis or scarring.

Imaging studies

Your doctor is also likely to order imaging tests, which can show whether you have fat in your liver or liver scarring. These may include:

Imaging tests also may be used to determine whether you have nodules or lumps in your liver.

The only conclusive test for NASH is a liver biopsy. A biopsy will show whether you have severe liver disease, and it rules out other liver diseases. During a biopsy, a doctor takes a sample of tissue from your liver and sends it to the pathology laboratory, where it’s examined under a microscope.

How NASH is treated

The U.S. Food and Drug Administration hasn’t approved medications to treat NASH. Research is underway to develop drugs that could treat this condition.

  • To reduce fat in your liver, try to lose weight if you’re currently overweight or obese. Aim for at least 3 percent to 5 percent of your body weight, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
  • Being active, even if you don’t lose weight, can also help treat NASH.
  • It’s important to treat related conditions, including diabetes, high blood pressure and high cholesterol. It’s also recommended that you don’t drink alcohol if you have NASH.

NASH can lead to cirrhosis. Cirrhosis can lead to complications, some of which can be treated with medications. If cirrhosis leads to liver failure or liver cancer, you may need a liver transplant.

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