In Normal Girls and Boys, Body Mass Index (BMI) Subsets Reveal Energy Priority of Trunk Width Growth and in the Limbs of Boys: Central Mechanisms May Have Enabled Human Bipedalism which, in Dysfunction, Predisposed Girls to AIS

摘要

Introduction: Skeletal growth is tightly coupled to energy balance via complex mechanisms involving leptin and hypothalamus. BMI is probably a surrogate measure for circulating leptin levels. Normal adolescent girls and boys age 11-18 years (n=555) with relatively higher BMIs show significantly greater trunk width growth, but only boys show this phenomenon also in limb lengths. Objectives: To evaluate normal juvenile children for skeletal lengths by BMI subsets.rnMaterials and Methods: Normal children age 5-10 years were measured using Holtain equipment for skeletal lengths by one observer (girls 172, boys 178). The data are analysed by higher and lower BMI subsets relative to median BMI values for age and sex (ANOVA correcting for age).rnResults: Compared between these BMI subsets, skeletal sizes by age for girls and boys respectively are (right limbs): biiliac width <0.001, <0.001; biacromial width 0.021, <.001, lengths of upper arm 0.213, 0.015, forearm-with-hand 0.224, 0.002, tibia 0.611, 0.098; foot 0.119, <0.001, corrected standing height 0.470, 0.011, corrected sitting height 0.247, <0.001; subischial height 0.838, 0.165. Conclusion: As in adolescents, juvenile girls with higher relative to lower BMIs show greater growth in trunk widths, but scarcely in limb lengths, and in juvenile boys both trunk widths and limb lengths. Growth plate mechanisms that determine this sexual dimorphism may include intrinsic receptor responses to hormones and/or extrinsic central (hypothalamic) mechanisms (leptin/sympathetic nervous system, SNS).rnSignificance: We suggest that normal trunk width growth is hormonally- and SNS-driven. The latter, provided energy priority that enabled human/hominin bipedalism which, in dysfunction, has predisposed girls to AIS.