Abnormal liver function in thyroid disorders may be secondary to thyrotoxicosis or to autoimmune injury to the liver. We report the case of a 36-year-old female who developed jaundice and pruritus with mild cholestasis and moderately elevated transaminase levels. The diagnosis of Graves' disease was made shortly thereafter. Laboratory findings were: alanine and aspartate aminotransferase 219 (IU/I (N: 9-50) and 102 IU/I (N: 10-15) respectively, alkaline phosphatase 336 IU/I (N: 40-135), bilirubin 24 micromol/I (N: 2-23), and gamma-glutamyl transpeptidase 232 IU/I (N: 9-43). Abdominal ultrasonography showed normal bile ducts; echocardiography ruled out heart failure; viral and autoimmune markers for hepatitis and cirrhosis were negative. Percutaneous liver biopsy showed moderate intrahepatic steatosis, anisokaryosis, lymphocyte infiltration in the portal areas, and Kupffer cell hyperplasia. Outcome was favorable after seven months of iodine therapy, confirming the diagnosis of thyrotoxicosis hepatitis.