Insulin secretion and insulin sensitivity in normal pregnancy and gestational diabetes mellitus.

The purpose of this study was to evaluate insulin sensitivity, beta-cell function and islet-cell-directed autoimmunity in pregnant women with normal glucose tolerance and gestational diabetes mellitus (GDM). A total of 21 women with normal glucose tolerance and 21 women with GDM were evaluated at 24-36 weeks' gestation. Insulin resistance and beta-cell function were evaluated using the continuous infusion of glucose with model assessment (CIGMA) method, which aims to give a near-physiological stimulus and to evaluate the endogenous insulin and glucose response. Islet-cell autoantibody was positive in one woman with GDM, and glutamic acid decarboxylase autoantibodies were negative in both groups. The calculated CIGMA insulin resistance (CIGMA IR) was 2.04 +/- 1.74 and 1.08 +/- 1.22 in patients with GDM and in control subjects, respectively (p < 0.05). CIGMA percentage beta-cell values were 64.04 +/- 44.55% and 87.07 +/- 52.77% in patients with GDM and control subjects, respectively (p > 0.05). Decreased insulin sensitivity in late pregnancy was more evident in lean GDM subjects with mild hyperglycemia who did not require insulin therapy, and beta-cell function was partially preserved in this group of patients.