A 38-year-old man presented with jaundice and significant weight loss. Investigations found positive hepatitis B surface antigen (HBsAg). His hepatitis B e antigen (HBeAg) was negative and HBV DNA was not detectable in the blood. Further tests revealed that he also had acute hepatitis E infection and uncontrolled thyrotoxicosis. The hypercatabolic state of coexisting thyrotoxicosis and acute hepatitis caused marked weight loss and clinical deterioration with fulminant hepatic failure. Institution of successful anti-thyroid treatment and supplemental nutrition effectively reversed the disease progression and the patient recovered fully.