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Physical growth of children treated for phenylketonuria
M A McBurnie1, R A Kronmal, V E Schuett
1Department of Biostatistics, University of Washington, Seattle.
Insights
Children treated for phenylketonuria (PKU) show different growth patterns than national standards, particularly in weight. Diet adherence appears to influence weight, with higher phenylalanine levels linked to increased weight in PKU patients.
Area of Science:
- Pediatric Endocrinology
- Metabolic Disorders
- Growth and Development
Background:
- Phenylketonuria (PKU) is a metabolic disorder requiring dietary management.
- Growth patterns in children treated for PKU require ongoing assessment against general population standards.
Purpose of the Study:
- To compare the growth of children treated for PKU with National Center for Health Statistics (NCHS) data.
- To identify specific growth parameters (height, weight, head circumference) that differ between PKU and non-PKU children.
Main Methods:
- Analysis of height, weight, and head circumference data from 133 children with PKU (ages 2-10).
- Comparison with NCHS growth curves using statistical tests (t-tests) and polynomial growth curves.
- Correlation analysis between serum phenylalanine levels and growth parameters.
Main Results:
- PKU children's height-for-age was similar to NCHS standards (around 50th percentile).
- PKU children, especially those over 3 years, showed higher weight-for-age and weight-for-height (between 50th-75th percentiles).
- Higher serum phenylalanine levels in PKU patients correlated with increased weight, particularly in girls.
Conclusions:
- Growth in treated PKU children deviates from national standards in weight, but not height.
- Diet adherence is a critical factor influencing weight status in children with PKU.
- Further research into the relationship between diet adherence and overweight tendencies in PKU is warranted.
Abstract:
The growth of 133 children participating in the Collaborative Study of Children Treated for Phenylketonuria (PKU) was compared to growth data from the National Center for Health Statistics (NCHS) to determine whether the growth patterns of the children with PKU were the same as those of unaffected children. Height and weight by age, and weight by height, were analysed for ages 2-10 years. Head circumference by age was analysed for ages 2-7 years. Median height by age of the PKU children was consistently near the 50th percentile of the NCHS growth curves for males and females. However, for both sexes, median weight by height and by age was between the 50th and 75th percentiles for children over 3 years old. Two-sample t-tests showed mean weight was significantly different (p less than 0.05) between the PKU and NCHS groups at most ages for both sexes. Median head circumference for the PKU children tended to be smaller than NCHS standards; however, the maximum difference at any age was less than 0.5 cm. Polynomial growth curves fitted to the PKU and NCHS growth data showed that, on average, the PKU males and females weighed more than their unaffected counterparts, while height and head circumference for both groups were very close. Including median serum phenylalanine (phe) level (mg/dl) in the growth curves suggested that the weight differences between the PKU and NCHS groups are related to degree of diet adherence. Higher phe levels in the PKU group were associated with higher weight levels, more so for girls (p less than 0.001) than for boys (p = 0.08). No relationship was found between phe level and height or head circumference. We conclude that growth in children treated for PKU differs from national standards for weight by age and weight by height, but not for height by age. We speculate that diet adherence may be an important factor in determining which children have a tendency to become overweight.