Metabolic Dysfunction-Associated Steatohepatitis (MASH) Overview

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe and progressive liver disease that develops from excess fat accumulation in the liver, leading to inflammation and scarring1 . It is part of a broader condition known as metabolic dysfunction-associated steatotic liver disease (MASLD), which affects over 30% of adults worldwide and is becoming a leading cause of liver-related complications, including liver cancer1 2. Early detection and management of MASH are critical to prevent progression to cirrhosis and other serious health outcomes3 .

MASH Symptoms

MASH is often called a "silent" disease because it usually causes no symptoms in its early stages3 4. Many people with MASH feel fine and are unaware they have the condition until liver damage becomes advanced. When symptoms do appear, they tend to be non-specific and may include:

Upper abdominal discomfort or pain, especially in the right upper belly area3 4
Fatigue or general weakness4
Unexplained weight loss4

As MASH progresses and liver fibrosis (scarring) worsens, more severe symptoms related to liver dysfunction may develop, such as:

Jaundice, a yellowing of the skin and eyes3 4
Ascites, which is swelling in the abdomen due to fluid buildup3
Easy bruising or bleeding caused by impaired blood clotting3
Swelling in the legs and spider-like blood vessels under the skin4
Enlarged spleen and changes in skin color on the palms4

Because early MASH symptoms are subtle or absent, regular checkups are important for individuals with risk factors to detect liver disease before complications arise3 .

MASH Causes and Risk Factors

MASH develops when excess fat builds up in liver cells (hepatocytes), causing inflammation and damage1 3. This fat accumulation is often linked to metabolic dysfunction, including problems with how the body processes sugar and fat. The exact mechanisms leading to MASH are complex and not fully understood but involve insulin resistance and chronic inflammation3 .

Risk Factors

Several metabolic and demographic factors increase the risk of developing MASH:

Obesity, particularly with a body mass index (BMI) greater than 303 5
Type 2 diabetes and metabolic syndrome, which includes high blood pressure, high blood sugar, and abnormal cholesterol levels3 2
Rapid weight loss, which can paradoxically worsen liver inflammation3
Age over 50 years, with incidence rising in older adults3
Ethnicity, with higher prevalence in Hispanic and Asian populations3
Genetic predisposition and environmental factors also contribute, though not all individuals with risk factors develop MASH2
Other associated conditions include polycystic ovary syndrome, obstructive sleep apnea, hypothyroidism, and growth hormone deficiency6

MASLD may be partly genetic and partly environmental. Most people who develop MASLD have at least one of these risk factors, but not everyone2 .

Diagnosing MASH

MASH is often detected incidentally during routine blood tests or physical examinations because early disease is asymptomatic3 5. Diagnosis requires a combination of clinical evaluation, laboratory tests, imaging, and sometimes liver biopsy.

Key diagnostic steps include:

Medical history focusing on metabolic risk factors, alcohol use, medications, and diet3
Physical examination for signs such as hepatomegaly (enlarged liver), jaundice, and BMI calculation3
Blood tests assessing liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST]), lipid profiles, and markers of inflammation3 4
Imaging studies such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) to visualize liver fat and fibrosis3 5
Non-invasive liver stiffness measurements using transient elastography (FibroScan) or magnetic resonance elastography (MRE) to assess fibrosis severity3 57

Liver biopsy remains the gold standard for confirming MASH diagnosis and staging fibrosis but is performed selectively due to its invasive nature and risks3 5. Biopsy involves microscopic examination of liver tissue to detect fat accumulation, inflammation, and scarring3 .

Stages of MASH

MASH progresses through stages defined by the extent of fibrosis:

Fibrosis Stage	Description	Clinical Significance
F0–F1	No or mild fibrosis	Early disease, often asymptomatic5
F2	Moderate fibrosis	Increased risk of progression5
F3	Advanced fibrosis	High risk of cirrhosis and complications5
F4	Cirrhosis (severe scarring)	Risk of liver failure, cancer, and death3
Sources: 12345

Approximately 20% of MASH cases progress to cirrhosis, which greatly increases the risk of liver cancer and liver failure3 5.

MASH Treatment Options

Currently, there is no cure for MASH, but treatment focuses on preventing progression and managing metabolic risk factors. Treatment strategies include lifestyle changes, medications, and surgery.

Lifestyle Approaches

Lifestyle modification is the cornerstone of MASH management and prevention3 58. Key interventions include:

Weight loss through a balanced, calorie-controlled diet low in sugar and saturated fats3 8
Regular physical activity, aiming for 150 to 300 minutes of moderate-intensity exercise per week3 2
Avoidance or limitation of alcohol intake to reduce liver stress2 8
Management of diabetes, high cholesterol, and hypertension to improve metabolic health3 5

Weight loss of 7–10% of body weight can reduce liver fat, inflammation, and fibrosis, potentially reversing early MASH2 6.

Medication

Pharmacological treatment options for MASH have been limited until recently. The first FDA-approved drug specifically for MASH with moderate to severe fibrosis is resmetirom, a thyroid hormone receptor-β agonist9 1011.

Resmetirom is indicated for adults with non-cirrhotic MASH and fibrosis stages F2 or F38 7
It works by reducing liver fat and inflammation, improving fibrosis, and has demonstrated safety and tolerability in clinical trials9 108
Resmetirom is prescribed alongside lifestyle modifications11 8
Other medications targeting metabolic comorbidities, such as GLP-1 receptor agonists for diabetes and obesity, are used to improve overall metabolic health but are not specifically approved for MASH treatment5 8
Non-incretin weight-loss agents are not recommended as MASH-targeted therapies8

Surgery

Bariatric surgery may be considered for patients with obesity and advanced liver disease3 5. Surgical options such as gastric bypass or sleeve gastrectomy can:

Promote significant and sustained weight loss5
Improve or even reverse liver damage caused by MASH5
Reduce the risk of progression to cirrhosis, liver cancer, and the need for liver transplantation5

Surgery is typically reserved for patients who do not respond adequately to lifestyle and medical therapies.

Preventing MASH

Prevention of MASH focuses on maintaining metabolic health and avoiding liver injury1 32. Key preventive measures include:

Maintaining a healthy weight through balanced diet and regular exercise3 2
Avoiding excessive alcohol consumption and hepatotoxic medications3
Managing metabolic conditions such as diabetes, high blood pressure, and high cholesterol3 2
Regular screening for liver disease in individuals with metabolic risk factors to enable early intervention5 12

Adopting these lifestyle habits not only prevents MASH but also reduces the risk of cardiovascular disease and other metabolic complications2 .

The Delphi panel revealed that approximately 75% of MASH patients in Germany remain undiagnosed. Non-invasive measures, such as fibrosis scores, liver enzyme tests, and liver stiffness measurement, were primary methods for diagnosing and monitoring MASH patients. Lifestyle modifications were the primary management strategy, given the absence of approved pharmacological treatments for MASH. The panel also highlighted significant challenges in managing MASH, including the lack of approved medications and the difficulty in sustaining lifestyle changes5 .

MASH is closely associated with several metabolic and systemic conditions, reflecting its role as the hepatic manifestation of metabolic syndrome1 32. Related conditions include:

Obesity and medically complicated obesity5
Type 2 diabetes and prediabetes3 5
Metabolic syndrome, including hypertension and dyslipidemia3 2
Cardiovascular diseases such as coronary artery disease and heart failure3 2
Chronic kidney disease3
Extrahepatic malignancies including colorectal, stomach, and pancreatic cancers2
Neurological complications like depression and neurocognitive dysfunction2
Endocrine disorders such as thyroid dysfunction and polycystic ovary syndrome2
Respiratory conditions like obstructive sleep apnea2

Managing these comorbidities is essential to improving overall outcomes in patients with MASH5 .

Every year, about 11,000 new cases of liver cancer related to MASLD and MASH are diagnosed. While other causes of liver cancer have decreased, MASLD is becoming more common2 .

Managing Life with MASH

Living with MASH requires ongoing medical care and lifestyle management to prevent disease progression and complications3 2. Without treatment, MASH can lead to:

Cirrhosis, characterized by extensive liver scarring and impaired liver function3
Hepatocellular carcinoma (liver cancer), with increased risk in cirrhotic patients3 2
Liver failure, which may necessitate liver transplantation3
Increased risk of cardiovascular events such as heart attack and stroke3 2

Early diagnosis and treatment improve prognosis and quality of life. Patients are encouraged to maintain healthy habits, adhere to medical therapies, and attend regular follow-ups for monitoring liver health3 2.