A longitudinal study of plasma insulin and glucagon in women with previous gestational diabetes

To investigate whether plasma insulin or glucagon predicts later development of diabetes in women with gestational diabetes mellitus (GDM).

The subjects studied were 91 women with diet-treated GDM and 33 healthy women. Plasma insulin and glucagon during a 50-g oral glucose tolerance test (OGTT) were measured during pregnancy, postpartum, and at follow-up 5-11 years later. At follow-up, the women were also examined with a 75-g OGTT or an intravenous glucagon test.

Twenty-seven (30%) of the women with previous GDM had abnormal glucose tolerance at follow-up (2 had insulin-dependent diabetes mellitus, 13 had non-insulin-dependent diabetes mellitus, and 12 had impaired glucose tolerance). Compared with the control subjects, women with previous GDM had relatively impaired insulin secretion (decreased insulinogenic index and delayed peak insulin response) at all time points investigated; this was also found when only nonobese glucose-tolerant women were examined. Low insulin secretion during pregnancy together with a high fasting plasma glucose level at the diagnostic OGTT in pregnancy and hyperglycemia during the postpartum OGTT were predictive for subsequent development of overt diabetes (logistic regression analysis).

Women who develop GDM have a relative insulin secretion deficiency, the severity of which is predictive for later development of diabetes. Furthermore, our data indicate that their relatively reduced beta-cell function may be a significant pathogenic factor in relation to the high incidence of subsequent diabetes in women with GDM. This could be important in the design of follow-up programs for women with previous GDM.