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NASH — non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis — the inflammatory form of fatty liver disease

NASH — inflammation and scarring of the fatty liver

NASH — non-alcoholic steatohepatitis (MASH in the new nomenclature) — is an aggressive, progressive form of NAFLD. Inflammation and ballooning degeneration of hepatocytes are added to fatty steatosis, which gradually scars the liver.

NASH is a variety of steatohepatitis not related to alcohol. It is NASH, rather than "simple" steatosis, that determines the risk of fibrosis, cirrhosis and liver cancer.

Why it develops

NASH is underpinned by metabolic dysfunction: obesity (especially abdominal), insulin resistance, type 2 diabetes, lipid disorders, hypertension. In 2023 the term was updated to MASH, emphasizing the link specifically with cardiometabolic factors.

A diagnosis of MASLD/MASH is made when there is fat in the liver plus at least one cardiometabolic factor (for example, an elevated BMI, prediabetes or diabetes, high triglycerides, low HDL, hypertension).

Why it is dangerous

NASH is the driver of progression: it leads to fibrosis, cirrhosis and hepatocellular carcinoma and has already become one of the leading reasons for liver transplantation. At the same time, the main cause of death in these patients is cardiovascular disease.

It is the stage of fibrosis, rather than the presence of fat, that best predicts outcomes, so it is assessed first.

Diagnosis and treatment

The starting point is non-invasive assessment of fibrosis (the FIB-4 index, elastography), and where it is uncertain — a biopsy. The basis of treatment is a loss of at least 10% of body weight, treatment of diabetes (including GLP-1 agonists) and of cardiovascular factors.

For NASH with moderate/marked fibrosis (F2–F3), the first approved drug has appeared — resmetirom.

Calculate using this marker

Calculators where NASH is used directly:

FIB-4 (Liver Fibrosis) A first-line check for liver scarring, adjusted for age Open NAFLD Fibrosis Score (NFS) Assesses advanced fibrosis in NAFLD from simple labs and BMI Open Fibrosis-NAFLD Index (FNI) Screens for fibrotic NASH from three labs in metabolically at-risk patients Open NAFLD Liver Fat Score Predicts fatty liver disease with a focus on insulin and metabolism Open

Frequently asked questions

How does NASH differ from NAFLD?

NAFLD is the entire spectrum of fatty liver disease, including harmless simple steatosis. NASH is its inflammatory, progressive form with cell damage and a risk of fibrosis and cirrhosis.

Can NASH be treated?

Yes, the key is weight loss and metabolic control, which can clear the inflammation and stabilize fibrosis. For stages F2–F3, drugs have also appeared (resmetirom).

Related terms

NAFLD / MAFLD Non-alcoholic (metabolically associated) fatty liver disease Steatosis Fatty degeneration of the liver Steatohepatitis Fatty liver with inflammation Liver fibrosis Scarring of the liver — the replacement of healthy tissue by connective tissue Cirrhosis The extreme stage of liver fibrosis with irreversible tissue restructuring Insulin resistance Reduced sensitivity of cells to insulin Metabolic syndrome A cluster of cardiometabolic risk factors Type 2 diabetes mellitus Persistently high sugar due to insulin resistance and a relative lack of insulin

Sources

  1. StatPearls (NCBI) — Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)
  2. AASLD — New MASLD Nomenclature
  3. American Liver Foundation — Nonalcoholic Steatohepatitis (NASH)
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This content is educational and does not replace consultation with a physician. Reference ranges may vary depending on the laboratory and method — rely on the ranges stated on your own test report.
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