Background: N-terminal parathyroid hormone-related protein has a vital role in regulating cell growth and differentiation, uteroplacental vasodilatation, uterine muscle relaxation, and placental transport. These functions are compromised in intrauterine growth restriction. We aimed to investigate N-terminal parathyroid hormone-related protein concentrations in maternal, fetal, and neonatal plasma of intrauterine-growth-restricted and appropriate for gestational age pregnancies.
Methods: Plasma N-terminal parathyroid hormone-related protein levels were determined in 40 mothers and their 20 intrauterine-growth-restricted and 20 appropriate for gestational age singleton full-term fetuses and neonates on postnatal days 1 and 4.
Results: Fetal N-terminal parathyroid hormone-related protein levels were significantly lower in the intrauterine growth restriction group (b=1.166, 95%CI: 0.430-1.902, p=0.003) and correlated with the customized centiles of the infants (r=0.407, p=0.009). In the appropriate for gestational age group, neonatal day 1 N-terminal parathyroid hormone-related protein levels were significantly lower compared to maternal (p<0.001) and fetal (p=0.022) ones. Fetal and neonatal day 1 levels were significantly lower in males (b=-1.303, 95%CI: -2.508 to -0.097, p=0.036, and b=-0.802, 95%CI: -1.5 to -0.105, p=0.027, respectively). In the intrauterine growth restriction group, maternal N-terminal parathyroid hormone-related protein levels were significantly increased compared to fetal (p<0.001) and neonatal day 1 (p=0.001) levels.
Conclusions: The reduced fetal N-terminal parathyroid hormone-related protein concentrations in intrauterine growth restriction may reflect compromised placental function and impaired fetal growth, suggesting that N-terminal parathyroid hormone-related protein may be involved in the pathogenesis of intrauterine growth restriction.