BONE TURNOVER IN NEONATES - CHANGES OF URINARY-EXCRETION RATE OF COLLAGEN TYPE-I CROSS-LINKED PEPTIDES DURING THE FIRST DAYS OF LIFE AND INFLUENCE OF GESTATIONAL-AGE

New markers have been used to monitor the changes of bone turnover occ urring during growth, Data on bone turnover rate during the perinatal period are, however, very scarce, In the present study we evaluated bo ne turnover rate, assessed by the measurement of urinary N-terminal te lopeptide of type I collagen (NTx) concentrations, at different gestat ional ages, and we documented the trend of bone turnover rate occurrin g in the first days after birth, Urine samples were obtained from 83 h ealthy full term newborn infants, 16 preterm, and 17 infants of diabet ic mothers (IDMs), The first miction after birth was collected, Urine samples were also collected 24 and 48 h after birth, NTx was measured by an enzyme-linked immunosorbent assay (Osteomark(R), Ostex Internati onal, Inc, Seattle, WA), The relationship between NTx at birth and all the other variables has been evaluated using multiple regression anal ysis, The changes of NTx excretion over time and the effect of the gro ups were studied by multivariate analysis of variance (MANOVA) for rep eated measures, We found a remarkable association between gestational age and NTx concentrations at birth (R = 0.56; p < 0.00001), NTx conce ntrations showed a progressive decrement, reaching a nadir between the 38th and the 42nd week of gestation, The NTx concentrations changed s ignificantly during the first 48 h of life in the three groups, Moreov er, preterm infants had NTx excretion values at birth significantly hi gher than full term infants (p < 0.001), whereas NTx excretion rates o f IDMs were not different from those of the other two groups of subjec ts, In conclusion, gestational age seems to be the major determinant o f bone turnover in neonates; NTx excretion rate is higher before term, it slows in proximity of delivery, and it increases significantly dur ing the first 48 h of life. Preterm infants have higher bone turnover rate than full term infants, NTx excretion rate of IDMs was comparable with those of the control subjects. (C) 1997 by Elsevier Science Inc.