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Urinary hydroxyproline: relationship to growth, bone mineral content, and serum alkaline phosphatase level in
F R Greer1, X R Chen, A McCormick
1Department of Pediatrics, Center for Health Sciences, University of Winconsin, Madison.
Insights
Urinary hydroxyproline (UHP) excretion increases with growth in premature infants. This marker strongly correlates with weight and length gain, indicating its utility in assessing somatic growth in this population.
Area of Science:
- Biochemistry
- Pediatrics
- Neonatology
Background:
- Limited data exists on urinary hydroxyproline (UHP) excretion in premature infants.
- UHP is a marker of collagen turnover, relevant to bone and tissue growth.
Purpose of the Study:
- To investigate the correlation between UHP excretion and somatic growth in premature infants.
- To explore relationships between UHP excretion, serum alkaline phosphatase, and bone mineral content (BMC).
Main Methods:
- Twenty-six premature infants (<1300g birth weight, ≤32 weeks gestational age) were studied.
- Infants received one of four feeding regimens.
- Measurements included UHP excretion, serum alkaline phosphatase, BMC, and growth parameters over 7 weeks.
Main Results:
- UHP excretion significantly correlated with absolute weight (r=0.64) and rate of weight gain (r=0.50).
- UHP excretion also correlated with absolute length (r=0.41) and rate of length gain (r=0.70).
- No significant correlation was found between UHP excretion and BMC or serum alkaline phosphatase.
Conclusions:
- UHP excretion is elevated in growing premature infants compared to older populations.
- UHP excretion serves as a reliable indicator of somatic growth in premature infants.
Abstract:
There is little information on urinary hydroxyproline (UHP) excretion in premature infants. We hypothesized that UHP excretion would positively correlate with growth in premature infants, and that there would be correlations between UHP excretion and serum alkaline phosphatase concentration as well as bone mineral content (BMC). Twenty-six premature infants (birth weight, less than 1,300 g; gestational age, less than or equal to 32 weeks) received one of four oral feedings. Seven received mother's own milk (HM), and eight received mothers own milk fortified with 0.85 g/dl of bovine whey, 90 mg/dl of Ca, and 45 mg/dl of P. Six and five infants received Similac, 20 cal/oz (SIM) and Similac Special Care, 20 cal/oz, respectively. Measurements of UHP, serum alkaline phosphatase, BMC (photon absorptiometry), and growth were made during the 1st 7 weeks of life. The lowest UHP excretion was in the HM group. For all infants, there was a significant correlation between UHP excretion (mg/day) and absolute weight (r = 0.64, p less than 0.001), as well as rate of weight gain (r = 0.50, p less than 0.01). The UHP excretion (milligrams per day) also correlated with absolute length (r = 0.41, p less than 0.01) and rate of gain in length (centimeters per week) (r = 0.70, p less than 0.001). The UHP excretion did not correlate significantly with BMC or serum alkaline phosphatase concentration. We conclude that UHP excretion is increased in the growing premature infant compared to older infants and adults and is a good marker for somatic growth in this population.(ABSTRACT TRUNCATED AT 250 WORDS)