Non-alcoholic fatty liver disease (NAFLD) is the accumulation of excess fat in the liver in the absence of significant alcohol use. It is the most common liver disease in the United States, affecting approximately 25% of the adult population. NAFLD is closely linked to metabolic conditions like obesity, Type 2 diabetes, insulin resistance, and metabolic syndrome — making it a condition where endocrinologists play a central role.

The Spectrum of NAFLD

NAFLD exists along a spectrum of severity:

  • Simple steatosis (fatty liver): Fat accumulation alone; generally benign; can regress with lifestyle change
  • MASH (Metabolic Dysfunction-Associated Steatohepatitis): Fat plus inflammation and liver cell damage; can progress to fibrosis. Previously called metabolic dysfunction-associated steatohepatitis (MASH).
  • Fibrosis: Scar tissue formation; grades F0–F4
  • Cirrhosis: Advanced scarring with loss of normal liver function; F4 fibrosis; risk of liver failure and hepatocellular carcinoma

Approximately 20–25% of patients with MASH develop cirrhosis. NAFLD/MASH is now a leading indication for liver transplant.

Risk Factors and Associations

NAFLD is the hepatic manifestation of metabolic syndrome. Key associations include:

  • Obesity (especially central adiposity): ~75% of obese adults have NAFLD
  • Type 2 diabetes: ~70% of T2D patients have NAFLD
  • Insulin resistance
  • High triglycerides and low HDL
  • Hypothyroidism
  • PCOS
  • Genetic factors (PNPLA3, TM6SF2 gene variants)

Symptoms and Diagnosis

NAFLD is usually asymptomatic until advanced. It is most often discovered incidentally through elevated liver enzymes (ALT, AST) on routine blood work or fatty liver seen on ultrasound or other abdominal imaging.

Assessment of fibrosis severity is critical because it determines prognosis. Non-invasive methods include:

  • FIB-4 score: Calculated from age, ALT, AST, and platelet count — a simple initial screening tool
  • Vibration-controlled transient elastography (FibroScan): Measures liver stiffness non-invasively; widely used for fibrosis staging
  • Liver biopsy: The gold standard; used when non-invasive tests are indeterminate

Treatment

Until recently, no pharmacological therapy was specifically approved for MASH. This has changed:

  • Lifestyle modification: Weight loss of ≥7–10% reduces hepatic steatosis, inflammation, and fibrosis; even 3–5% reduces fat content. Exercise independently improves liver health.
  • Resmetirom (Rezdiffra): The first FDA-approved medication specifically for MASH with moderate-to-advanced fibrosis (F2–F3); a thyroid hormone receptor beta agonist that reduces liver fat and improves fibrosis in clinical trials
  • Metabolic treatments: GLP-1 agonists (semaglutide) and SGLT-2 inhibitors show significant benefits for NAFLD/MASH — they also treat the underlying metabolic drivers
  • Manage contributing conditions: Optimize blood sugar, lipids, blood pressure, and thyroid function

Key Takeaways

  • NAFLD affects 25% of Americans — it's the most common liver disease, closely linked to metabolic syndrome
  • MASH (formerly metabolic dysfunction-associated steatohepatitis (MASH)) is the progressive form that can lead to cirrhosis
  • 7–10% weight loss significantly improves liver disease at all stages
  • Resmetirom (Rezdiffra) is the first FDA-approved medication specifically for MASH
  • GLP-1 agonists and SGLT-2 inhibitors treat both NAFLD and its metabolic causes
Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before making any changes to your treatment plan. Individual medical decisions should be made in partnership with your physician based on your specific circumstances.