Inclusion criteria:  Postmenopausal women 45-70 years old NASH by biopsy or NAFLD by imaging within 6 months of screen Hepatitis C antibody and hepatitis B surface antigen negative Negative mammogram within 1 year  Exclusion criteria:  Heavy alcohol use Use of NASH pharmacotherapies within 12 months of study entry Known cirrhosis, stage 4 fibrosis on biopsy, or clinical evidence of cirrhosis or portal hypertension on imaging or exam Participation in NASH clinical trial within 6 months of study entry Chronic use of corticosteroids, methotrexate, amiodarone, or tamoxifen within 6 months of entry Known diagnosis of chronic liver disease other than NAFLD or found on biopsy Contraindication to liver biopsy including INR > 1.5, platelets < 50,000/mL, ascites, chronic anticoagulation (other than aspirin), biliary obstruction, peritonitis, inability to lie supine for 30 minutes Hgb < 10.0 g/dL or glomerular filtration rate < 60 mL/min Contraindications to estrogen therapy Any vaginal bleeding, including spotting, within the last year Active malignancy Severe chronic illness Use of estrogen or progesterone within a year of baseline visit Routine MRI exclusion criteria such as the presence of a pacemaker or cerebral aneurysm clip