Overview.
Metabolic dysfunction-associated steatotic liver disease (MASLD) — formerly called NAFLD — is the most common liver condition worldwide, affecting approximately 25-38% of adults globally. It encompasses a spectrum from simple hepatic fat accumulation (steatosis) to active liver inflammation and cell injury (MASH, formerly NASH), progressive fibrosis, cirrhosis, and liver cancer. MASLD is driven by insulin resistance and metabolic dysfunction, making it a liver manifestation of the broader metabolic syndrome. The condition is frequently discovered incidentally through elevated liver enzymes on routine blood tests.
MASLD develops when excess fat accumulates in liver cells (hepatocytes), primarily driven by insulin resistance. In susceptible individuals, this triggers oxidative stress, mitochondrial dysfunction, and gut dysbiosis-driven inflammation — a cascade that can lead to MASH (steatohepatitis with hepatocyte injury and lobular inflammation). Progressive fibrosis then follows through hepatic stellate cell activation. The 2023 multisociety Delphi consensus renamed NAFLD to MASLD, reflecting the central role of metabolic risk factors, and introduced the MASLD/MetALD/MASH nomenclature framework (Rinella ME et al., 2023; PMID: 37364790).
Prevalence: Affects 25-38% of adults globally — approximately 1 in 3 people. Prevalence rises sharply in those with metabolic risk factors: ~75% in obesity, ~69% in type 2 diabetes. Incidence is rising worldwide, with a 50% relative increase from 1990 to 2019. More common in men (36.6%) than women (25.5%).
Medical name: Metabolic Dysfunction-Associated Steatotic Liver Disease
Symptoms.
Early warnings
- Mildly elevated ALT or AST on routine blood tests with no obvious cause
- Elevated GGT without significant alcohol use
- Liver steatosis (fatty appearance) reported on abdominal ultrasound
- Fatigue and right upper quadrant discomfort (many patients are asymptomatic)
Classic symptoms
- Most patients are asymptomatic in early stages — MASLD is a 'silent' liver disease
- Fatigue (most common symptom when present)
- Right upper quadrant discomfort or heaviness
- Signs of metabolic syndrome: central obesity, acanthosis nigricans
- In advanced disease / cirrhosis: jaundice, ascites, oedema, confusion (hepatic encephalopathy)
Progression
The MASLD spectrum: steatosis (F0) → steatohepatitis (MASH) → fibrosis (F1-F4) → cirrhosis → hepatocellular carcinoma. Only ~20% of patients with steatosis develop MASH; of those, ~20-30% progress to advanced fibrosis over 10-15 years. Annual fibrosis progression rate is ~0.1 stages in MASLD vs ~0.3 stages in MASH. Cirrhosis-related complications (ascites, variceal bleeding, hepatic encephalopathy) and hepatocellular carcinoma represent end-stage complications. Cardiovascular disease — not liver disease — is the leading cause of death in MASLD patients at most fibrosis stages.
Risk factors.
- Obesity or overweight (BMI ≥25 kg/m²)
- Type 2 diabetes mellitus or insulin resistance
- Metabolic syndrome (hypertension, dyslipidaemia, central obesity, impaired glucose)
- Elevated triglycerides or low HDL cholesterol
- Hypothyroidism (independent risk factor)
- Polycystic ovary syndrome (PCOS)
- Family history of fatty liver disease or cirrhosis
- South Asian and Hispanic ethnicity (higher genetic predisposition)
Lab interpretation.
Key biomarkers
- ALT (Alanine Aminotransferase) — Typically 1-3x ULN; can be normal even in MASH (normal ALT does not exclude significant liver disease) (primary)
- AST (Aspartate Aminotransferase) — Often elevated; AST:ALT ratio >1 suggests more advanced fibrosis or significant alcohol use (primary)
- GGT (Gamma-Glutamyl Transferase) — Sensitive but non-specific; elevated early in MASLD; correlates with insulin resistance and metabolic syndrome severity (primary)
- Fasting Glucose / HbA1c — Elevated in majority of MASLD patients; T2DM / insulin resistance is the central driver (primary)
- Fasting Insulin / HOMA-IR — Elevated HOMA-IR (>2.5) indicates clinically significant insulin resistance; central to MASLD pathogenesis (primary)
- Triglycerides — Frequently elevated (>150 mg/dL); part of MASLD cardiometabolic diagnostic criteria (secondary)
- HDL Cholesterol — Often low; part of MASLD metabolic criteria; low HDL + elevated triglycerides = dyslipidemia pattern (secondary)
- Platelet Count — Thrombocytopenia develops with portal hypertension / cirrhosis; used in FIB-4 calculation (secondary)
Diagnostic criteria
- Hepatic steatosis confirmed by imaging (ultrasound, MRI-PDFF) or histology
- At least 1 of 5 cardiometabolic risk factors: BMI ≥25, impaired fasting glucose/T2DM, hypertension, elevated triglycerides, low HDL (2023 MASLD definition)
- Exclusion of other causes: significant alcohol use, medications (corticosteroids, tamoxifen, amiodarone), viral hepatitis, autoimmune hepatitis, Wilson's disease
- Fibrosis staging: FIB-4 score as first-line non-invasive test (AASLD 2023)
- FIB-4 >1.3: add FibroScan (VCTE) or ELF as secondary fibrosis assessment
- FIB-4 >2.67 or liver stiffness ≥9.7 kPa: refer to hepatology
Recommended panels
When & next steps.
When to test
- Elevated ALT, AST, or GGT on routine blood tests without other obvious cause
- Ultrasound report showing 'echogenic liver' or 'fatty liver'
- Type 2 diabetes or prediabetes (screen for MASLD-related fibrosis with FIB-4)
- Metabolic syndrome: obesity, hypertension, dyslipidaemia
- Unexplained fatigue with metabolic risk factors
- PCOS with liver enzyme elevation
- Hypothyroidism with persistently elevated transaminases
If suspected
- Order: ALT, AST, GGT, bilirubin, albumin, platelets, fasting glucose, HbA1c, lipid panel
- Exclude other liver diseases: hepatitis B (HBsAg), hepatitis C (anti-HCV), ferritin (iron overload), ANA/ASMA (autoimmune), caeruloplasmin if young
- Calculate FIB-4 score (requires: age, ALT, AST, platelet count)
- Abdominal ultrasound confirms steatosis; note that ultrasound can miss mild steatosis (<30%)
- If FIB-4 <1.3: reassure, manage metabolic risk factors, recheck liver enzymes + FIB-4 every 1-2 years
If confirmed
- Lifestyle modification is foundational: 7-10% body weight loss reduces hepatic fat; >10% loss can achieve MASH resolution
- Aggressive management of metabolic comorbidities: T2DM (GLP-1 agonists preferred), hypertension, dyslipidaemia
- GLP-1 receptor agonists (semaglutide): strong evidence for MASH resolution; AASLD 2025 guidance supports use
- Resmetirom (Rezdiffra): FDA-approved March 2024 for MASH with moderate-advanced fibrosis (F2-F3)
- If FIB-4 ≥1.3: FibroScan to stage fibrosis; hepatology referral if FIB-4 >2.67
- Hepatocellular carcinoma surveillance (ultrasound ± AFP every 6 months) if cirrhosis confirmed
- Avoid hepatotoxic medications and supplements; alcohol abstinence or minimal use
FAQs.
My ultrasound showed a 'fatty liver' — does that mean I have MASLD?
An ultrasound showing echogenic (bright) liver texture suggests hepatic steatosis, which is the characteristic finding of MASLD. However, ultrasound cannot distinguish simple steatosis from MASH (the more serious inflammatory form), and it misses mild steatosis. Your doctor will combine the imaging result with your blood tests (ALT, AST, GGT, metabolic markers) and calculate your FIB-4 score to assess for fibrosis and determine management.
What is the FIB-4 score and why does it matter?
FIB-4 is a non-invasive scoring tool calculated from your age, AST, ALT, and platelet count. It estimates your risk of having advanced liver fibrosis (scarring). The AASLD 2023 guideline recommends FIB-4 as the first-line test for all patients with suspected MASLD. A FIB-4 below 1.30 means low risk — you can be monitored in primary care. A FIB-4 above 2.67 means high risk — you should be referred to a hepatologist for further assessment.
Can I reverse fatty liver?
Yes — in the early stages (steatosis and mild fibrosis), MASLD is reversible with sustained lifestyle changes. A 7-10% reduction in body weight significantly reduces hepatic fat. Greater than 10% weight loss can achieve MASH resolution and even fibrosis regression. GLP-1 receptor agonists like semaglutide also show strong clinical trial evidence for MASH resolution and are now supported by AASLD guidelines.
Can I have MASLD with normal liver enzymes?
Yes. Normal ALT does not exclude significant MASLD or even MASH. Studies show that up to 25-40% of patients with biopsy-confirmed MASH have normal ALT levels. This is why FIB-4 calculation and risk factor assessment are important even when liver enzymes appear normal — especially in patients with metabolic syndrome, type 2 diabetes, or obesity.