Insulin receptors on erythrocytes in normal and obese pregnant women: comparisons to those in nonpregnant women during the follicular and luteal phases.

Insulin receptors on erythrocytes were studied in nonpregnant women (n = 14) during the follicular and luteal phases, and in pregnant women in the third trimester with normal body weight (n = 14), with weight gain over 14 kg during pregnancy (n = 7), and with obesity before pregnancy (n = 7). Women with increased reticulocytes in the blood were excluded from this study. Insulin binding was slightly decreased in nonpregnant women during the luteal phase, as compared with the binding during the follicular phase. Insulin binding in normal pregnant women was comparable to that in nonpregnant women during the luteal phase. The number of receptors was reduced in those women who gained an excessive amount of body weight during pregnancy or in those pregnant women who were previously obese. These results suggest that an increased insulin resistance during pregnancy, compared to the luteal phase in nonpregnant women, cannot be explained by the changes in insulin receptors but that the reduction in insulin receptors might be one of the causes of the deterioration in carbohydrate metabolism in obese women in late pregnancy.