Multivariate Analysis Of The Association Between Obesity And Girls With Idiopathic Central Precocious Puberty

Background:There is a correlation between increasing prevalence of obesity and earlier pubertal development in girls.The impact of body mass index on sexual hormones of stimulation test in ICPP girls had been discussed recently,but the results were controversial.The aim of this study was to investigate the multiple factors affecting stimulation test and the relationship between BMI and the hormones of stimulation test after adjusting confounding factors,the independent effect of BMI on the indicators of stimulation test was also analyzed.Study design:Cross-sectional study.Patients:618 girls diagnosed with ICPP were stratified according to age-matched BMI,355 girls were normal weight,99 girls were overweight and 164 girls were obese.Results:Univariate regression and multiple regression analysis were combined first to figure out multiple factors affecting the levels of hormones in stimulation test.Generalized linear regression model was set to investigate the linear and non-linear relationship between BMI-SDS and indexes of stimulation test,with confounding factors adjusted.There was a significant negative correlation between BMI-SDS and LH peak in the normal weight group(P:-16.1,95%CI = 31.1-1.1,P = 0.038).The value of ? in overweight group was much higher than that of normal weight group.A threshold effect of BMI-SDS had been found in the obese group.The trend of linear relationship between BMI-SDS and LH basal value was not significant in normal and overweight groups.In the obese group,non-liner relationship between BMI-SDS and LH basal values showed a threshold at(BMI-SDS<2.7,?:-1.2,95%CI =-2.2,-0.2,P = 0.024 vs.BMI-SDS>2.7,p:0.2,95%CI =-0.5,0.9,P =0.543).BMI-SDS was negatively correlated with the basal FSH,and FSH peak,threshold effect had been found in overweight groups.Conclusion:The levels of stimulation test may be affected by the adrenergic androgen and sex hormones,as well as insulin in ICPP.A non-linear relationship and independent threshold effects could be found between BMI-SDS and several indicators of stimulation test.The strongest correlation between the stimulated test hormone values,especially the LH peak existed in overweight group.We speculate that in ICPP,access adiposity itself have independent inhibitory effect on LH secretion.This effect deeper as obesity developed and may convert to a promoting effect(LH peak)after reaching the threshold point of BMI-SDS.Background:Serum vitamin D status in Children is affected by obesity and the status of vitamin D can be associated to several diseases.Recently,association of vitamin D deficiency with menarche and puberty timing has been documented.Through this study,we intend to explore the relationship between serum 25-OH-D and ICPP and how obesity affecting vitamin level in ICPP patients.Objects:In this study,a total of 280 girls diagnosed as idiopathic central precocious puberty(ICPP)and 188 age-matched control girls of normal puberty were enrolled.Results:The ICPP group had significantly lower serum 25-hydroxyvitamin D(25-OH-D)level compared with its age-matched controls.Furthermore,a nonlinear relationship had been found between 25-OH-D and ICPP,and there was a cut-off point for serum 25-OH-D of 31.8 ng/mL for ICPP with and without different confounding factors adjusted.Girls with serum 25-OH-D ?31.8 ng/mL had a lower odds ratio(unadjusted:OR = 0.36,95%CI:0.15 to 0.83,P<0.05;height and weight adjusted:OR=0.44,95%CI:0.18 to 1.08,P=0.072;BMI adjusted:OR=0.36,95%CI:0.16 to 0.84,P<0.05).When ICPP subjects were divided into three groups according to vitamin D status we found that ICPP subjects with 25-OH-D deficiency had greater BMI than the other two subgroups,the basal LH and basal FSH in 25-OH-D deficiency group was also higher than the other two groups.Correlation regression analysis showed that vitamin D level had a negative correlation with BMI and BMI-SDS.Further analysis showed non-linear relationship between BMI-SDS and 25-OH-D,and a threshold effect of BMI-SDS at 3.3 had been found.Conclusion:Our study suggest that vitamin D status may be associated with the risk of ICPP and may have a threshold effect to ICPP.There was a threshold effect of obesity to 25-OH-D in ICPP patients.