Analysis of serum osteocalcin in neonates at different gestational age

Introduction: Little is known about fetal bone metabolism. Osteocalcin (Oc), synthesized by osteoblasts most actively in early fetal life, has been a marker of bone turnover. The aim of this study was to measure osteocalcin levels in neonates of different gestational age to evaluate bone metabolism in the fetus. Subjects and Methods: A total of 107 neonates composed of 30 fullterm (FT) and 77 preterm (PT) infants was enrolled in this study. Blood samples were collected in the first 24-hours and biweekly after birth. Fluoroimmunoassay (Pharmacia CAP system, Uppsala, Sweden) was employed for detecting the serum osteocalcin level. Results: The mean osteocalcin level in all 107 cases was 6.133 ± 7.202 ug/L, in the FT group 9.430 ± 10.390 ug/L, and in the PT group 4.848 ± 5.018 ug/L. The difference between the LnOc in the FT and PT groups approached significance (p=0.056). Osteocalcin was positively associated with birth body weight (BBW) (coefficients = 0.00042, p < 0.01) and gestational age (GA) (coefficients = 0.0801, p < 0.01) by linear regression, which yielded estimated regression equations of LnOc = BBW* 0.00042 + 0.297 and LnOc = GA *0.0801-1.591, respectively. There was no significant difference between genders. A subset of fourteen preterm infants was followed for longitudinal changes in the osteocalcin level. A rapid increase at one month after birth was found. Conclusion: In this study, serum osteocalcin in neonates increased with GA and BBW. This might indicate that fetal bone metabolism increases in late fetal life.