Gestational diabetes mellitus (GDM) affects 2%-4% of the all pregnant women, and it is a major risk factor for development of type 2 DM. We performed this cross-sectional study to determine whether there were defects in insulin secretory capacity or insulin sensitivity in women with previous GDM.

On 6-8 weeks after delivery, 75 g oral glucose tolerance test was performed in 36 women with previous GDM and 19 non-pregnant control women matched with age and weight. Intravenous glucose tolerance test was performed on 10-14 weeks after delivery. Insulin secretory capacity measured as the acute insulin response to glucose (AIRg) and insulin sensitivity as minimal model derived sensitivity index (S_I) were obtained. AIRg×S_I (β-cell disposition index) was used as an index of β-cell function.

Women with previous GDM were classified into normal glucose tolerance (postpartum-NGT, n=19) and impaired glucose tolerance (postpartum-IGT, n=17). Postpartum fasting glucose levels were significantly higher in postpartum-IGT compared to postpartum-NGT and control (P<0.05). AIRg×S_I was significantly lower in postpartum-IGT compared to control (P<0.05). S_I was lower in postpartum-NGT and postpartum-IGT compared to control, but the difference did not have the statistical significance. Frequency of parental history of type 2 diabetes was significantly greater in postpartum-IGT compared to postpartum-NGT (P<0.05).

Women with previous GDM showed impaired insulin secretion although their glucose tolerance states were restored to normal. It suggests impaired early insulin secretion may be a major pathophysiologic factor for development of type 2 DM, and this defect may be genetically determined.

Insulin resistance is a major pathophysiology in polycystic ovary syndrome (PCOS), and assessment of insulin sensitivity is important. Various insulin sensitivity indices from fasting state or oral glucose tolerance test (OGTT) have been compared with euglycemic hyperinsulinemic clamp. We aimed to evaluate the usefulness of these indices in young Korean women with PCOS.

Euglycemic hyperinsulinemic clamp test and 75 g OGTT were performed in 290 women with PCOS. Insulin mediated glucose uptake (IMGU), the insulin sensitivity index from clamp, was compared with various insulin sensitivity indices such as composite insulin sensitivity index (ISI_comp), estimated metabolic clearance rate (MCR_est) of glucose and estimated insulin sensitivity index (ISI_est), area under the curve of glucose and insulin ratio (AUC-GIR), OGTT-derived Belfiore index, and oral glucose insulin sensitivity index (OGSI) by Kazama. Fasting state indices such as glucose insulin ratio (GIR), homeostasis model assessment for insulin resistance (HOMA-IR), fasting Belfiore index, and quantitative insulin sensitivity check index (QUICKI) were also compared with IMGU.

The correlation coefficients of ISI_comp, MCR_est, ISI_est, AUC-GIR, OGTT-Belfiore index, and OGSI with IMGU were all about 0.5 (Ps'<0.001) in PCOS women as a whole. The MCR_est and ISI_est were significantly correlated with IMGU in both obese (r=0.58 and 0.58, P<0.0001) and non-obese subjects (r=0.33 and 0.32, P<0.001). Fasting glucose and insulin-derived indices showed worse correlation with IMGU than OGTT-derived ones.

The MCR_est and ISI_est from OGTT might be the best replacement for the insulin sensitivity index from hyperinsulinemic euglycemic clamp independent of obesity.