The insulin-like growth factor system and Type 1 diabetic retinopathy during pregnancy

AIMS/HYPOTHESIS: To find out whether the levels of insulin-like growth factor-I (IGF-I), IGF binding protein-1 (IGFBP-1), highly phosphorylated IGFBP-1 (hpIGFBP-1), and IGF binding protein-3 (IGFBP-3) are related to the progression of diabetic retinopathy (DR) during pregnancy and postpartum. METHODS: In a prospective study of 42 pregnant women with Type 1 diabetes and 9 nondiabetic controls, DR was graded from fundus photographs. Levels of serum total IGF-I and two different phosphoisoform patterns of IGFBP-1 and IGFBP-3 were measured during the first and third trimester of pregnancy and 3 months postpartum. RESULTS: Both the levels of serum total IGF-I (P<.0001) and IGFBP-3 (P=.003) were lower in the diabetic than in the nondiabetic women during pregnancy and postpartum (repeated-measures ANOVA between the groups). Additionally, the IGF-I and IGFBP-3 levels tended to be lower in the diabetic women with more severe DR at baseline than in those with less severe DR. There were no statistically significant differences in the levels of IGF-I and IGFBP-3 in the diabetic women with progression of DR compared with those without. No statistical differences appeared in the IGFBP-1 phosphoisoform patterns between the groups. CONCLUSIONS/INTERPRETATION: In diabetic women, mean serum levels of IGF-1 and IGFBP-3 are lower than in nondiabetic controls during pregnancy and/or postpartum. Because there was no clear connection between the IGF system and progression of DR during pregnancy, it is unlikely that these substances mediate the tendency of DR to progress during pregnancy.