A Case of Insulinoma Presenting As Circadian Rhythm Sleep Disorder

• Published in: Nihon Kyukyu Igakukai Zasshi 2007/02/15, Vol.18(2), pp.47-50
• Main Authors: Ito, Takeshi, Komura, Masayoshi, Miyatake, Satoru, Shinozaki, Hiroharu, Arai, Kunihiko, Yokoyama, Mizue, Kobayashi, Kenji
• Format: Article
• Language: English
• Subjects: hypoglycemia; insulin; mental disorder; pancreatic tumor; somnolence
• ISSN: 0915-924X; 1883-3772
• DOI: 10.3893/jjaam.18.47

We report the case of a 17-year-old female first presenting as circadian rhythm sleep disorder, then later diagnosed as insulinoma. The patient demonstrated severe deterioration of academic performance in high school classes six months prior to examination. She also had disordered dietary habits, including copious late-night consumption progressing to reversal of daytime and nighttime activities. The patient was examined by a psychiatrist and diagnosed with circadian rhythm sleep disorder. Somnolence developed and worsened thereafter, and the patient was transported by ambulance to our facility. The patient was silent and almost non-verbal at admission, suggesting a mental disorder. However, hypoglycemia persisted despite the opportunity for adequate food intake after admission. Additional investigation and extensive test results showed an insulin/glucose ratio of 0.64 (17.8 μU/ml/28 mg/dl). Abdominal magnetic resonance imaging (MRI) demonstrated a 15 × 10 mm tumor at the border of the pancreatic head and body. Insulinoma was diagnosed, and the tumor was excised. Hypoglycemia and circadian rhythm sleep disorder disappeared completely after surgery, and the patient was discharged. The Japanese literature shows that approximately 10% of insulinomas present various mental symptoms. Chronic hypoglycemia symptoms are also sometimes difficult to differentiate from mental disorders, and careful observation is required in emergency room settings.