Leptin and bone turnover in monochorionic twins complicated by twin–twin transfusion syndrome

Introduction To test the hypothesis that the bone metabolism of a growth-restricted foetus is regulated by genetic, placental and/or foetal factors through leptin, we investigated the foetal bone turnover in monochorionic pregnancies complicated with or without twin–twin transfusion syndrome (TTTS). Methods Maternal and cord bloods were collected from gestational-age-matched monochorionic twins with ( n = 15) and without ( n = 15) TTTS. The samples were assayed for leptin, 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 by radioimmunoassay (RIA). Results In the growth-restricted donor twin, the plasma concentration of leptin ( P < 0.001), PICP ( P < 0.001) was lower, while that of ICTP ( P < 0.001) was higher than the recipient twin of the TTTS group. In contrast, leptin, PICP and ICTP were comparable in non-TTTS twins. In the recipient twin of TTTS and non-TTTS twins, leptin was positively associated with PICP ( r = 0.73; n = 45, P < 0.001) and negatively with ICTP ( r = −0.68; n = 45; P < 0.001). No such association was found between leptin and bone marker in the growth-restricted donor twin of the TTTS group. Conclusion Our data suggest that, in AGA twins, leptin maintains bone metabolism by inhibiting resorption and enhancing bone formation. In contrast, growth-restricted donor twins have high bone turnover and this does not seem to be due to leptin deficiency.