MASLD

MASLD stands for metabolic dysfunction-associated steatotic liver disease. It is the umbrella term adopted in 2023 to replace nonalcoholic fatty liver disease (NAFLD), and it designates the condition in which there is imaging or histologic evidence of hepatic steatosis together with at least one cardiometabolic risk factor (for example, elevated BMI, elevated fasting glucose or a diagnosis of type 2 diabetes, elevated blood pressure, or a dyslipidemia pattern). The rename was driven by several linked concerns: the word "nonalcoholic" defined the condition by what it was not; the term "fatty" was considered stigmatizing; and the diagnostic criteria did not directly tie the disease to its actual pathophysiologic driver, metabolic dysfunction. The consensus statement is Rinella et al., Hepatology 2023 (NLM 37363821).

MASLD, MetALD, and MASH in relation to each other

Under the 2023 nomenclature, MASLD sits at the top of a disease spectrum. A subgroup of individuals with MASLD who also meet defined thresholds for alcohol intake are classified as having MetALD (metabolic and alcohol-associated liver disease). The subgroup of MASLD whose histology shows lobular inflammation and hepatocyte ballooning in addition to steatosis is MASH. The spectrum therefore runs from simple steatosis (MASLD without steatohepatitis) through MASH and onward to fibrosis, cirrhosis, and hepatocellular carcinoma in those who progress. Noninvasive tools for identifying MASLD and for stratifying fibrosis risk are reviewed in Rinella et al., Hepatology 2023 (NLM 37363821) and in the AASLD practice guidance for NAFLD Chalasani et al., Hepatology 2018 (NLM 28714183).

Why MASLD is a useful index term

A great deal of published research on GLP-1 receptor agonists, FGF21 analogs, thyroid hormone beta-selective agonists, and other metabolic candidates reports liver-fat and liver-enzyme outcomes in populations defined by MASLD (or, in older literature, NAFLD) criteria. Indexing research peptides under MASLD therefore allows a reader to locate the disease-context citations for a molecule without conflating research findings in that population with any claim about an RUO research reagent.

Open Assay's treatment

Open Assay uses MASLD as the current consensus term in new content, preserves NAFLD as the term of art in pre-2023 citations, and links the two so a reader can follow the scientific record across the nomenclature change. Peptide listings that cite MASLD research do so at the level of the published source, not as a claim about the reagent itself.