Objective: We investigated the relationship between IGF-I-IGFBP-1 and leptin levels with type 1 collagen markers of bone turnover in dichorionic (DC) twins with or without discordant birth weight of 20%.

Methods: Maternal and cord bloods were collected from gestational age matched DC twins with (n = 16) or without (n = 16) discordant birth weight The samples were assayed for cross linked carboxyl terminal telo-peptide (ICTP, a marker of bone resorption) and pro-peptide (PICP, a marker of bone formation) of type I collagen, leptin, IGF-1 and IGFBP-1 by radio-immunoassay.

Results: The growth restricted twins (IUGR) of discordant group had higher fetal ICTP (P < 0.001) and IGFBP-1 (P < 0.001) levels, while PICP (P < 0.001), IGF-1 (P < 0.001) and leptin (P < 0.001) were lower than the co-twins with normal weight (AGA). In contrast, concentrations of IGF-1, IGFBP-1, ICTP, PICP and leptin were comparable between concordant twin pairs. Leptin levels were positively correlated with PICP (r=0.61; P < 0.001) and negatively with ICTP (r= -.57; P < 0.001) in concordant and AGA twins but not in IUGR twins. In IUGR twins, IGF-1 had positive association with PICP (r=.76; P < 0.001) and negative with ICTP (r= -.76; P < 0.001), while IGFBP-1 was negatively correlated with PICP levels (r=-.65; P < 0.01). No such association was found in concordant and AGA twins.

Conclusion: These data suggest that growth restricted twins had high bone turnover which is independent of maternal factors and perhaps may be due to altered IGF axis.