Insulin secretion and insulin resistance in Korean women with gestational diabetes mellitus and impaired glucose tolerance

Background/Aims: The aim was to compare the insulin sensitivity and secretion index of pregnant Korean women with normal glucose tolerance (NGT), gestational impaired glucose tolerance (GIGT; only one abnormal value according to the Carpenter and Coustan criteria), and gestational diabetes mellitus (GDM). Methods: A cross-sectional study was performed with 1,163 pregnant women with positive (1-hour plasma glucose ${\geq}$ 7.2 mmol/L) in a 50-g oral glucose challenge test (OGCT). The 100-g oral glucose tolerance test (OGTT) was used to stratify the participants into three groups: NGT (n = 588), GIGT (n = 294), and GDM (n = 281). Results: The GDM group had higher homeostasis model assessment of insulin resistance and lower insulin sensitivity index ($IS_{OGTT}$), quantitative insulin sensitivity check index, homeostasis model assessment for estimation of index ${\beta}$-cell secretion (HOMA-B), first and second phase insulin secretion, and insulin secretion-sensitivity index (ISSI) than the NGT group ($p{\leq}0.001$ for all). Moreover, the GIGT group had lower ISOGTT, HOMA-B, first and second phase insulin secretion, and ISSI than the NGT group (p < 0.001 for all). Among the GIGT subjects, the 1-hour plasma glucose abnormal levels group showed significantly greater weight gain during pregnancy and higher values in the 50-g OGCT than the other two groups. Moreover, the 1-hour and 2-hour abnormal levels groups had poorer insulin secretion status than the 3-hour abnormal levels group. Conclusions: Korean women with GDM show impairments of both insulin secretion and insulin sensitivity. In addition, GIGT is associated with both ${\beta}$-cell dysfunction and insulin resistance.