Subclinical abnormalities of glucose metabolism in Brazilian women with a history of gestational diabetes mellitus

The objective was to evaluate insulin release and insulin sensitivity in women with prior gestational diabetes mellitus (GDM) to gain a better understanding of type 2 diabetes pathogenesis. GDM women were individually matched for age body mass index and waist/ hip ratio with those who were normal glucose tolerant in a previous pregnancy (NGT). All women presented with normal glucose tolerance. Twenty pairs were submitted to the oral glucose tolerance test (OGTT) with plasma glucose insulin and C-peptide determinations. Of the 20 pairs 18 participated in hyperglycemic (10.0 mmol/l) clamp experiments with frequent plasma glucose and insulin determinations allowing us to calculate first and second-phase insulin release and the insulin sensitivity index. GDM and NGT women were compared using Student’s t-test the Mann–Whitney U-test Friedman’s nonparametric test and the two proportion test for independent groups. GDM women showed higher glycosylated hemoglobin values; at OGTT they showed late insulin peak with increased plasma insulin levels only during the second hour and a similar plasma C-peptide response despite a higher plasma glucose curve; during hyperglycemic clamp procedures they showed similar biphasic insulin release and insulin sensitivity index. Considering that a woman with previous GDM had a defect in insulin release and/or insulin sensitivity if its magnitude was at least 25% lower than that of the matched NGT woman 43.8% showed impairment of first-phase insulin release and 55.6% insulin resistance. GDM women showed some degree of glucose intolerance. It is therefore necessary to follow them for a longer time. (authors)