Etiology	Clinical clues	Initial diagnostic testing
Common
Alcohol-related	Excessive alcohol consumption	Aspartate transaminase/alanine transaminase ratio, γ-glutamyl transpeptidase level
Hemochromatosis	Family history	Serum iron and ferritin levels, total iron-binding capacity
Hepatitis B	Immigration from endemic countries, nonmonogamous sexual activity, injection drug use	Hepatitis B surface antigen testing
Hepatitis C	Injection drug use, human immunodeficiency virus infection, blood transfusion before 1992	Hepatitis C virus antibody testing
Medications	Polypharmacy, certain herbal preparations	History
Nonalcoholic fatty liver disease	Evidence of metabolic syndrome (high triglyceride levels, low high-density lipoprotein levels, increased waist circumference, elevated glucose levels)	Fasting lipid profile, glucose level; consider ultrasonography
Less common
α1-antitrypsin deficiency	Early-onset emphysema, family history	Serum α1-antitrypsin level
Autoimmune hepatitis	Women with autoimmune disorders	Serum protein electrophoresis; antibodies to liver/kidney microsomal antibody type 1, antinuclear antibody, and smooth muscle antibody testing
Wilson disease	Younger than 40 years, neuropsychiatric symptoms, Kayser-Fleischer rings	Serum ceruloplasmin level
Extrahepatic
Celiac disease	Diarrhea, abdominal pain, malabsorption	Tissue transglutaminase antibody testing
Hemolysis	Glucose-6-phosphate dehydrogenase deficiency, sickle cell anemia, infection	Lactate dehydrogenase and haptoglobin levels, reticulocyte count
Muscular disorders	Muscle weakness and pain, strenuous exercise	Creatine kinase and aldolase levels
Thyroid disorders	Signs and symptoms of hypo- or hyperthyroidism	Thyroid-stimulating hormone level