Insulin-like growth factors (IGF) I and II in diabetic pregnancy: Suppression of normal pregnancy-induced rise of IGF-I

Abstract

The concentrations of somatomedins/insulin-like growth factors were measured by a specific radioimmunoassay for insulin-like growth factor-I and a specific radioreceptor assay for insulin-like growth factor-II in sera of term normal and Type 1 (insulin-dependent) diabetic pregnant women and in various cord sera of their newborn infants. Serum insulin-like growth factor-I levels in normal (non-diabetic) maternal serum were higher than in non-pregnant women (486 ± 26 versus 215 ± 26 ng/ml). The normal pregnancy-induced increment of insulin-like growth factor-I was markedly reduced in diabetic pregnancy. It was not different in patients with good or poor glycaemic control, as judged by normal or elevated blood levels of haemoglobin A_1c content. Insulin-like growth factor-I levels in cord serum of infants of diabetic women with good glycaemic control (86±11 ng/ml) and poor glycaemic control (91±19 ng/ml) were significantly higher (p < 0.01) than in infants of non-diabetic women (43±42 ng/ml). The fetal birth weight ratios were not significantly correlated with insulin-like growth factor-I levels in cord serum. Serum insulin-like growth factor-II levels in maternal and cord serum in diabetic and normal pregnancy were not different from each other or from normal non-pregnant women. The increment in insulin-like growth factor-I levels in maternal serum in pregnancy may influence placental structure and function. Lack of this increment in maternal diabetes may have direct implication in placental abnormalities in diabetes and indirect implications on fetal development and metabolism. The increment in fetal serum insulin-like growth factor-I levels in infants of diabetic mothers might suggest a role for insulin-like growth factor-I in fetal macrosomia. This finding, along with the lack of correlation with maternal glycaemic control, might suggest that fetal hyperinsulinaemia has a greater role than insulin-like growth factor-I in the fetal macrosomia. Serum insulin-like growth factor-II levels do not appear to be influenced by pregnancy or diabetes. The similar levels of insulin-like growth factors-I or II in normal and diabetic non-pregnant women may present some evidence against a major role of both insulin-like growth factors in the chronic complications which may develop in persons with diabetes.