1384-P: Changes in OGTT-Based Measures of Insulin Secretory Response across Pregnancy

Background: We previously showed that insulin response to an IV glucose load increases in early pregnancy, independent of changes in insulin sensitivity. It is unknown whether oral glucose tolerance test (OGTT)-based measures of insulin secretory response (ISR) capture the same phenomenon. Methods: This is a secondary analysis of a longitudinal study. Participants (N=31) were studied pre-pregnancy and in early (12-14 wks) and late (34-36 wks) gestation. On separate days, after overnight fasts, an OGTT (75g pre-pregnancy/100g in pregnancy) and an hyperinsulinemic-euglycemic clamp were performed. We calculated Insulinogenic index (IGI), Corrected insulin response (CIR), insulin/glucose area under the curve (AUCins/AUCglu), and Stumvoll 1st Phase Estimate (Stumvoll) from OGTT insulin and glucose levels. Linear mixed effects models examined ISR in early as compared to pre- and late pregnancy; we adjusted p-values for 2 comparisons. Adjusted models included insulin sensitivity, measured with the clamp, as a time-dependent covariate. Results: IGI (adjusted mean ± SEM) increased between pre- and early pregnancy (1.25 ± 0.13 vs. 1.52 ± 0.15, P