title: Urinary hydroxyproline in infants with and without fractures/rickets.
abstract: Molar ratios of peptide-bound and free hydroxyproline:creatinine (OHPr:Cr) in urine were measured at 3, 6, 9, and 12 months of age in two groups of very-low-birthweight (VLBW less than or equal to 1500 g) infants. Group A (15 infants) had radiographically confirmed fractures and (or) rickets (F/R); Group B (17 infants) did not. The urinary peptide-bound OHPr:Cr ratio varied widely within groups and was greatest at three months in both groups: A = 0.81 +/- 0.45 and B = 0.55 +/- 0.32 (mean +/- SD). The ratio decreased with increasing postnatal age for each group but was not statistically different between groups throughout the study. The urinary free OHPr:Cr ratio also was greatest at age three months (A = 0.32 +/- 0.15 and B = 0.53 +/- 0.46), rapidly decreasing afterwards, and was not statistically different between groups throughout the study. We conclude that, in VLBW infants, bone turnover as indicated by the urinary peptide-bound OHPr:Cr ratio is highest during early infancy; however, the wide range of values for this ratio suggests that its use alone is not sufficient for detection of F/R in VLBW infants. The rapid decrease in free OHPr:Cr ratio is presumably related to the maturation of renal tubular function.
authors.affiliation: Department of Pediatrics, University of Alberta Hospitals, Walter Mackenzie Health Science Centre, Edmonton, Canada.
authors.forename: W W
authors.initials: WW
authors.lastname: Koo
authors.forename: S K
authors.initials: SK
authors.lastname: Krug Wispe
authors.forename: P
authors.initials: P
authors.lastname: Succop
authors.forename: A
authors.initials: A
authors.lastname: Champlin
authors.forename: R
authors.initials: R
authors.lastname: Sherman
authors.forename: H
authors.initials: H
authors.lastname: Berry
mesh_terms: D001827:Body Height; D001835:Body Weight; D002352:Carrier Proteins / Q000652:urine; D003404:Creatinine / Q000652:urine; D005260:Female; D050723:Fractures, Bone / Q000150:complications / Q000000981:diagnostic imaging / Q000652:urine*; D006801:Humans; D006909:Hydroxyproline / Q000652:urine*; D007223:Infant; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D010455:Peptides / Q000652:urine; D011859:Radiography; D012279:Rickets / Q000150:complications / Q000000981:diagnostic imaging / Q000652:urine*
chemical_list: D002352:Carrier Proteins; D010455:Peptides; D003404:Creatinine; D006909:Hydroxyproline