Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by hepatic steatosis that is confirmed by imaging or histology in the setting of at least 1 metabolic risk factor in the absence of significant alcohol consumption. Nonalcoholic steatohepatitis, or NASH, was recently renamed metabolic dysfunction-associated steatohepatitis (MASH); it represents the progressive form of MASLD. MASH is defined by hepatic steatosis, lobular inflammation, and ballooning degeneration (hepatocellular injury) in a characteristic histologic pattern. Multiple pathophysiologic mechanisms underlie the development of MASLD, and multiple factors (eg, metabolic, hormonal, genetic, nutritional, and epigenetic components) are related to liver injury. MASH has a prevalence in the United States of 1% to 6%, and it is expected to rise in the next decade. Individuals living with MASH frequently suffer from comorbidities such as type 2 diabetes and cardiovascular disease. Several guidelines have been published to support the timely diagnosis of MASH that incorporate noninvasive tests that obviate the need for liver biopsy. Multiple MASH treatment options are in various stages of development. The THR-β agonist resmetirom, approved by FDA in March 2024, offers a liver-directed treatment for those patients living with moderate to severe fibrosis without cirrhosis. Considering the progressive nature of the disease and the availability of a treatment that can be initiated early to halt MASH progression, patients who have risk factors for MASH should urgently be encouraged to visit their health care providers for MASH screening.
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