Bone maturation along the spectrum from normal weight to obesity: a complex interplay of sex, growth factors and weight gain.

BACKGROUND: The aim of the study was to define the prevalence and degree of advanced bone age (ABA) in normal vs. excessive weight children, and identify variables affecting ABA.

METHODS: We studied 167 children (3-18 years) with normal weight (28 F, 28 M), overweight (8 F, 12 M), and obesity (OB) (63 F, 28 M) at AI duPont Hospital for Children. We assessed bone age (BA), insulin, leptin, estradiol (E2), DHEAS, and IGF-1 levels.

RESULTS: Almost 25% of OB children have ABA>2 SDS, 33% >2 years (range 2-6.5 years advanced). ABA correlated with leptin, DHEAS and BMI z-score in girls, and with IGF-1 z-score and BMI z-score in boys (p<0.01). Girls with ABA had higher BMI z-score (p<0.001), insulin levels (p=0.02), and rates of weight gain (p=0.03). Boys with ABA had greater BMI z-score (p<0.001), but rate of weight gain did not differ. The greatest degree of ABA was found combining variables by tertiles. The top tertile of BA/CA had the highest insulin and IGF-1 z-scores. The top combined tertiles of DHEAS and BMI z-score or DHEAS and leptin in girls had the highest BA/CA. In boys, the top tertiles of BMI z-score and IGF-1 z-score produced the highest BA/CA. The lowest combined tertiles of any variables related to the lowest BA/CA.

CONCLUSIONS: Multiple factors influence skeletal maturation. Almost 25% of children with OB have ABA, associated with BMI z-score, and one or more of the following: insulin, leptin, DHEAS, IGF-1, and rate of weight gain. This report delineates the prevalence and degree of ABA by sex, in children with normal versus excessive weight.