Insulin receptor binding to monocytes and erythrocytes during normal human pregnancy

In normal human pregnancy glucose tolerance deteriorates gradually in spite of a steady increase in plasma insulin levels. To see whether this change in insulin resistance is accompanied by changes in insulin receptor binding, insulin binding to monocytes and erythrocytes was measured serially during pregnancy and again post-partum in fifteen normal women. Insulin binding to monocytes increased from week 12 to week 24 of gestation (P less than 0.001) and it decreased from week 32 to week 36 (P less than 0.05). After delivery a new increase in insulin binding to monocytes was seen (P less than 0.05). Insulin binding to erythrocytes increased from week 30-32 to week 36 (P less than 0.05), decreased from week 36 to delivery (P less than 0.01) and decreased further post-partum (P less than 0.001). Insulin receptor binding was not significantly correlated to plasma insulin, estradiol, estriol, progesterone or cortisol. The insulin receptor binding to monocytes, but not to erythrocytes, paralleled the insulin resistance found in human pregnancy.