A case of insulinoma with non-alcoholic fatty liver disease: Roles of hyperphagia and hyperinsulinemia in pathogenesis of the disease

Nonalcoholic fatty liver disease (NAFLD) is a serious health-related condition all over the world; the number of patients is increasing in Asian countries including Japan. Better understanding of its pathophysiology is required to develop effective therapeutics, as patients may go on to develop non-alcoholic steatohepatitis and hepatocellular carcinomas. While NAFLD is believed to be associated with metabolic risk factors such as obesity, diabetes, and dyslipidemia, its etiology remains largely unknown and the development or co-existence of NAFLD in patients with insulinoma has not been investigated. A 33-year-old male with an insulinoma, who had been hypoglycemic during the previous four years, developed abnormally elevated levels of liver enzymes and histological fatty liver characteristic of NAFLD by the time of admission to our hospital for resection of an insulinoma. His medical records for the previous eight years revealed that his bodyweight had increased gradually from 60 kg to 71 kg for seven years and then acutely increased to 79 kg in the latest one-year period. This sudden increase was thought to be due to the patient's self-described overeating of fruits to forestall hypoglycemia. Fresh fruits are rich in fructose, and the patient's triglycerides, alanine and aspartate transaminases showed an acute increase in the previous one-year period. After resection of the insulinoma, the levels of these parameters all were mostly restored, which suggests that hyperinsulinemia and subsequent hyperphagia played a role in the development of NAFLD in this case. This is the first report of patient with NAFLD and an insulinoma.