Hypoglycemia Associated with a Gastrointestinal Stromal Tumor Producing High-molecular-weight Insulin Growth Factor II: A Case Report and Literature Review

: A 61-year-old woman with multiple metastatic and unresectable gastrointestinal stromal tumors (GISTs) was referred for investigation of refractory hypoglycemia that developed four months before this hospitalization. On admission, her fasting plasma glucose was 38 mg/dL despite 10% glucose infusion. Investigations revealed that her serum C-peptide, insulin and growth hormone levels were suppressed, and big insulin-like growth factor II was observed. She was diagnosed with non-islet cell tumor hypoglycemia, which resolved after glucocorticoid treatment. Clinicians should thus be vigilant to identify hypoglycemia in patients with large metastatic GISTs because glucocorticoid therapy is useful even if the GIST is inoperable.