Objective To investigate the reason for the appearance of bimodal insulin release curve (IRC).

Methods Sixty-three cases of bimodal pattern of IRC(double hump group)were selected as experimental group; 18 normal volunteers as control group.Oral glucose tolerance test, insulin release test and C-peptide release testwere performed, and the index of steady-state model was calculated.

Results There were no significant difference among the two groups in fasting insulin, 1 hC-peptide, fasting plasma glucose, Homa-insulin resistance.0.5 hIns: double hump group > control group.Fasting C-peptide: controll group > double hump group > normal Group.0.5 h C-peptide: double hump group and control group > normal group.Fasting plasma glucose: normal group > double hump group and control group.0.5 h plasma gulcose: normal group > double hump group > control group.glucose area under curve: normal group > double hump group > control group; △I₃₀/△G₃₀: double hump group > control group > normal group.insulin area under curve and C-peptide area under curve: double hump group > control group and normal group. There were significant difference among the results.

Conclusions The pancreatic island has an overcompensation in the first secretion phase in double hump group, and the insulin displayed the pseudopeak value at 0.5 h which lead to the increase of blood glucose.The pancreatic island has a normal peak value in the second secretion phase, the patients in this group exsits impaired glucose tolerance.