Metabolic Dysfunction-Associated Steatohepatitis, or MASH, is a progressive liver disease that develops when excess fat accumulation in the liver is accompanied by inflammation and cell damage. This condition was previously known as nonalcoholic steatohepatitis (NASH). The name was updated in 2023 to better reflect the disease’s strong connection to overall metabolic health.
MASH is the more severe form of metabolic dysfunction-associated steatotic liver disease (MASLD), which involves fat buildup in the liver without significant inflammation.
Associated Conditions and Risk Factors
MASH is closely linked to a cluster of metabolic issues and is considered a component of systemic metabolic dysfunction. It often occurs as part of metabolic syndrome, a group of conditions that increase the risk for heart disease, stroke, and type 2 diabetes. A diagnosis of metabolic syndrome requires having at least three specific risk factors.
The primary risk factors for developing MASH include:
- Obesity, defined by a body mass index (BMI) over 30, particularly with excess fat concentrated around the abdomen.
- Type 2 diabetes or insulin resistance, where the body’s cells do not respond properly to insulin.
- Dyslipidemia, which refers to abnormal levels of fats in the blood, such as high triglycerides and low high-density lipoprotein (HDL) cholesterol.
- High blood pressure, or hypertension.
The presence of multiple of these conditions substantially increases the likelihood of developing MASH.
Identifying and Diagnosing MASH
In its early stages, MASH is often a “silent disease” because it presents with few to no noticeable symptoms. When symptoms do appear, they are frequently vague, such as general fatigue, weakness, or a dull discomfort in the upper right abdomen. The diagnostic process often begins incidentally when routine blood tests reveal elevated liver enzymes, like alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
While elevated enzymes suggest liver inflammation, they are not a definitive indicator of MASH. These clues prompt further investigation to understand the cause of the liver stress. To visualize the liver and detect fat, healthcare providers use non-invasive imaging tests. An abdominal ultrasound is often the first step to identify steatosis, or fatty liver.
More advanced imaging methods may be used to gather detailed information. A FibroScan, a specialized ultrasound known as transient elastography, can measure both liver fat and stiffness, which indicates scarring (fibrosis). While blood tests and imaging provide strong evidence, a liver biopsy is the most accurate method for a definitive diagnosis. This procedure involves examining a small sample of liver tissue to confirm inflammation and cell damage.
Disease Progression and Potential Complications
If MASH is not managed, the continuous inflammation and injury can lead to the development of scar tissue, a process known as fibrosis. As fibrosis worsens, the scar tissue replaces healthy liver tissue, impairing the organ’s ability to function. The disease’s progression is measured in stages of fibrosis, and on average, it can take about seven years for fibrosis to advance one stage.
Stage 4, the most advanced stage of fibrosis, is called cirrhosis. At this point, the liver is severely scarred, which disrupts its structure and function. It is estimated that about 20% of individuals with MASH may progress to cirrhosis.
The development of cirrhosis is a serious turn that can lead to severe health problems. One of the major complications is liver failure, where the liver stops working correctly. Cirrhosis also significantly increases the risk of developing hepatocellular carcinoma, a type of primary liver cancer. MASH and its progression are also associated with a higher risk of cardiovascular events like heart attack and stroke.
Management and Treatment Strategies
Managing MASH centers on lifestyle modifications aimed at improving metabolic health and reducing stress on the liver. Weight loss is a primary goal, as losing 7-10% of total body weight can decrease liver fat, reduce inflammation, and sometimes reverse fibrosis. Dietary adjustments are a large part of the management plan.
Adopting a balanced, nutrient-dense eating pattern like the Mediterranean diet is often recommended. This approach emphasizes whole foods such as fruits, vegetables, lean proteins, and healthy fats while limiting processed foods, saturated fats, and sugars. Avoiding alcohol is also advised, as it can add stress to the liver.
Regular physical activity is another important component of managing MASH. A combination of aerobic exercises and resistance training is recommended, with a goal of 150 to 300 minutes of moderate-intensity exercise per week. This helps with weight management and improves the body’s sensitivity to insulin.
While lifestyle changes are the primary intervention, pharmacological treatments are also available. In 2024, the FDA approved resmetirom, the first medication specifically for MASH patients with moderate to advanced fibrosis. Other medications, such as GLP-1 agonists, may also be prescribed to reduce liver inflammation and fat. These treatments are used to complement, not replace, lifestyle modifications.