Characteristics of 72 h Glucose Profiles Detected by Continuous Glucose Monitoring System in Patients with Insulinoma

Objective To identify the characteristics of glucose profiles in patients with insulinoma using continuous glucose monitoring system (CGMS). Methods Six patients with insulinoma (All of the patients were diagnosed after operations with pathological tests) admitted to the Department of Endocrinology and Metabolism, West China Hospital of Sichuan University from October 2009 to November 2011 were recruited for this study (group A). They were compared with 71 patients with normal glucose tolerance（NGT）(group B) and 3 patients with responsive hypoglycemia (group C). All of the participants received 75 g oral glucose tolerance tests （OGTT）, insulin release tests, and 72 h CGM. Glucose fluctuations and hypoglycemia risks were assessed by the following parameters obtained from CGMS: mean blood glucose (MBG) and standard deviation (SD), mean amplitude of glycemic excursion (MAGE), mean daily differences (MODD), low glucose index (LBGI), glycaemic Risk Assessment Diabetes Equation (GRADE) and M-value. Results Group A had significantly lower levels of HbA1c, fasting blood glucose, and 2 h-BG than group B （P<0.05）. Compared with Group B, Group A had lower levels of 72 h-MBG（P<0.001） and higher levels of LBGI, M-value, GRADE, SD and MODD （P<0.05）. The insulinoma patients had 27 occasions of hypoglycemia (glucose<2.8 mmol/L), more likely in early morning, at a fasting state or preprandial periods. Such events were rare in the control groups (2 occasions in Group B and one occasion in Group C). Conclusion Insulinoma patients present a greater level of glucose fluctuations and frequent hypoglycemia. Hypoglycemia risk detected by CGM is helpful for differentiating diagnosis of insulinoma.