Objective: To investigate the state of insulin secretion and insulin resistance in patients of Graves disease (GD) with impaired glucose tolerance (IGT) by hyperglycemic clamp.
Methods: Six cases of Graves disease with IGT were selected as GD + IGT group and ten healthy volunteers as normal control group (NC group). All the subjects were required to fast for 12 hours and then underwent hyperglycemic clamp to assay insulin secretion and insulin sensitivity. Glutamic acid decarboxylase antibody (GAD-A) was tested in all the subjects.
Results: Insulin secretion in GD + IGT group was significantly higher than that in NC group. The 1st phase insulin secretion (1PH) was (636.31 +/- 105.54) mIU/L vs (233.56 +/- 21.33) mIU/L, P = 0.001. The 2nd phase insulin secretion (2PH) was (146.68 +/- 25.00) mIU/L vs (67.06 +/- 6.23) mIU/L, P = 0.03. The maximal insulin secretion during 120 - 150 minutes (Ins(120 - 150)) was (195.05 +/- 32.94) mIU/L vs (87.64 +/- 9.78) mIU/L, P = 0.04. The hyperglycemic clamp insulin sensitivity index (average glucose metabolic rate during 120 - 150 minutes/Ins(120 - 150)) was significantly lower in GD + IGT group than that in NC group (11.52 +/- 1.90 vs 21.72 +/- 3.25, P = 0.04). GAD-A was negative in all subjects.
Conclusion: Cases of GD with IGT show significant insulin resistance with compensated elevated insulin secretion.