Introduction: We reported evidence suggesting that in normal juveniles with relatively higher BMI, girls but not boys have central leptin resistance of the somatotropic axis. This may be a mechanism to limit the energy invested in female skeletal growth thereby conserving energy for reproductive development.
Objectives: To address upper arm length asymmetry (UALA) and its relation to skeletal size for age in the same normal juvenile children (girls 172, boys 178).
Materials and Methods: Girls and boys age 5-10 years are evaluated by higher and lower BMI subsets relative to median BMI values for: (1) UALA (right minus left, mm), and (2) standard deviation scores (SDSs) of 13 skeletal segments including stature, sitting height, trunk widths, upper and lower limbs, including UALs.
Results: SDSs of most skeletal segments for girls with lower BMI correlate significantly with UALA (girls 9/13, boys 1/13), and mostly not for higher BMI (girls and boys each 1/13). UALA in girls is significantly greater in lower than higher BMI subsets but not in boys.
Conclusion: The findings can be explained by somatotropic and sympathetic nervous system controls of some girls being linked in the hypothalamus and/or peripherally, leading to UAL sizes for age and UALA being associated to produce the statistically significant correlations.
Significance: This ULA/UALA study suggests that central (hypothalamic) controls for normal juvenile female skeletal growth may differ from normal juvenile boys. In dysfunction, this may explain why girls are predisposed to AIS more than boys as in our double neuro-osseous theory for AIS pathogenesis.