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Postnatal changes in serum osteocalcin and parathyroid hormone concentrations
J L Loughead1, F Mimouni, R Ross
1Department of Pediatrics, Perinatal Research Institute, University of Cincinnati College of Medicine, Ohio 45267-0541.
Insights
Cord clamping affects fetal calcium supply, leading to decreased serum calcium and increased parathyroid hormone (PTH) in newborns. This study shows a significant drop in serum osteocalcin (OC), a bone formation marker, within 24 hours of birth.
Area of Science:
- Neonatal physiology
- Endocrinology
- Mineral metabolism
Background:
- Cord clamping interrupts fetal calcium supply, potentially impacting neonatal calcium homeostasis.
- Neonatal parathyroid hormone (PTH) secretion increases postnatally, likely in response to hypocalcemia.
Purpose of the Study:
- To investigate the effect of cord clamping on neonatal bone formation markers.
- To assess changes in serum osteocalcin (OC) concentrations in the first 24 hours of life.
Main Methods:
- Measured serum ionized calcium (iCa), PTH, and OC in 26 neonates at birth, 2 hours, and 24 hours.
- Analyzed cord blood and serial blood samples from healthy newborns.
Main Results:
- Serum iCa significantly decreased postnatally, while serum PTH levels increased.
- Serum OC concentrations showed a sharp decline from cord blood to 2 hours, remaining stable thereafter.
- The reduction in OC correlated inversely with the rise in PTH.
Conclusions:
- Neonatal bone formation, indicated by serum OC, decreases significantly in the first 24 hours after birth.
- Elevated PTH levels may contribute to the observed decrease in bone formation markers postnatally.
Abstract:
Cord clamping at birth leads to interruption of calcium (Ca) supply to the fetus. After birth, neonatal parathyroid hormone (PTH) secretion appears stimulated by hypocalcemia, with serum PTH increasing after birth and peaking at 24 hours of age. This rise in PTH presumably leads to bone resorption and Ca release. We theorize that bone formation may also be affected and that a serum marker of bone formation, serum osteocalcin (OC) concentrations, will decrease postnatally. OC is synthesized by osteoblasts and its serum concentrations are believed to reflect bone formation. We measured serum ionized Ca (iCa), PTH, and OC in cord blood and at 2 and 24 hours in 26 neonates born after uncomplicated pregnancies, labors, and deliveries. Serum iCa (mg/dl) decreased from 5.79 +/- 0.06 (cord, means +/- SEM) to 5.31 +/- 0.05 (2 hr), then to 4.89 +/- 0.05 (24 hr) (p less than 0.05). Serum PTH (microliter Eq/ml) increased from 35.9 +/- 4.3 (cord) to 41.7 +/- 4.0 (2 hr) (p = 0.1), and to 50.3 +/- 4.6 (24 hr) (p less than 0.01). Serum OC (ng/ml) decreased from 55.1 +/- 10.6 (cord), to 12.4 +/- 4.3 (2 hr) (p less than 0.01), then remained stable at 12.7 +/- 1.9 (24 hr). The change (cord minus 24 hr) in OC correlated inversely with the change in PTH over the first 24 hours of age (r = -0.42. p = 0.03). Therefore, there is a sudden decrease in an index of bone formation (i.e., serum OC) in the first 24 hours of life in which rising serum PTH may have had an impact.(ABSTRACT TRUNCATED AT 250 WORDS)