Insulin Receptors in the Pregnant Diabetic and Her Newborn*

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Abstract
To ascertain if changes in the diabetic state during pregnancy were mediated by alterations in insulin receptors, we studied insulin receptors on monocytes and erythrocytes from 18 pregnant women with insulin-dependent diabetes (IDD) during the first and third trimesters. In the first trimester, insulin binding to both cell types was similar to that in normal nonpregnant women. Moreover, insulin receptor binding remained unchanged during the third trimester even in the face of the significantly increased insulin requirement and concomitant hyperinsulinemia. Our findings suggest that changes in insulin receptors are not primarily involved in alterations of diabetic control during pregnancy. Newborns of mothers with IDD have the appearance of fetal gigantism and often suffer from neonatal hypoglycemia. To determine whether altered insulin receptor binding might contribute to these phenomena, we studied insulin receptors on monocytes and erythrocytes in infants of normal mothers (n = 21) and mothers with IDD (n = 14). Compared to adults, insulin binding to both cell types from both categories of infants was significantly increased and to the same extent. The combination of fetal hyperinsulinemia and increased receptor binding in the presence of hyperglycemia may account, at least in part, for the accelerated growth of fetuses born of diabetic mothers. Finally, the enhanced neonatal glucose tolerance of these babies may be related not only to the hyperinsulinemia but also to increased insulin sensitivity mediated, in part, by the increased insulin receptor binding.