We have constructed a reference model to facilitate comparison of serum IGF-I values among children, and thereby to improve the value of IGF-I measurements for diagnosis. The data set consists of serum values measured in 969 samples from 468 healthy children and adolescents (232 males, 236 females; ages, 1.1-18.3 yr). One sample per child was used for the model, each being selected so as to provide sufficient observations for each stage of puberty. The samples not selected were used to validate the reference data. The IGF-I values were log transformed, and multiple regression analysis was used in the model-building process. The best linear model, which converts serum IGF-I concentrations into SD scores and explains 66% of the variation in logIGF-I values, includes the variables of age, gender, and puberty, and takes the interactions among these variables into account. In prepubertal and early pubertal children, the relationship between age and logIGF-I was positive, with greater effect in girls older than 8 yr. In mid-puberty, logIGF-I values were higher in girls than in boys of the same age, up to 16 yr of age. Among boys, the most pronounced positive relationship between age and logIGF-I occurred in mid-puberty, whereas the relationship between age and logIGF-I among girls in mid-puberty is fairly constant. In late puberty, logIGF-I values were higher than earlier in puberty, and there was a negative relationship with age in both boys and girls. Instead of separate models for each combination of puberty and gender, estimating a single regression model permits simultaneous estimation of all explanatory variables and uses all observations in the data set, thereby making it easier to select those variables that have a significant effect on logIGF-I. Our model shows that IGF-I levels are related to age during each stage of puberty. The model also accounts for the fact that serum IGF-I concentrations during puberty are different for boys and girls.

Background: Childhood BMI may influence subsequent growth in height as well as the timing of puberty. The aim of the present study was to investigate associations between BMI in childhood and subsequent height gain/pubertal growth. Methods: Longitudinal growth data were used (GrowUp 1990 Gothenburg cohort, n = 1,901). The QEPS growth-model was used to characterize height gain in relation to the highest BMI SDS value between 3.5 and 8 y of age. Children were defined as overweight/obese (OwOb) or normal weight/underweight (NwUw), using the 2012 International Obesity Task Force criteria. results: A negative association between childhood BMI SDS and pubertal height gain was observed. Already at birth, OwOb children were heavier than NwUw children, and had a greater height velocity during childhood. Onset of puberty was 3.5/3.0 mo earlier in OwOb girls/boys, and they had 2.3/3.1 cm less pubertal height gain from the QEPS-models specific P-function than NwUw children. Adult height was not related to childhood BMI. conclusion: We found that pubertal height gain was inversely related to peak BMI in childhood. Higher childhood BMI SDS was associated with more growth before onset of puberty, earlier puberty, and less pubertal height gain, resulting in similar adult heights for OwOb and NwUw children.

Almost all available sets of height growth reference values are constructed in a cross-sectional manner, except for a few studies in which longitudinal sampling was used. Such reference values are, however, flawed because of considerable individual variation in the timing of puberty, especially among children with early or late pubertal maturation. An additional complicating factor is that the magnitude of the total pubertal growth spurt is significantly larger among those individuals with early pubertal maturation, compared with late maturation. Based on the growth records of 145 healthy Swedish children followed longitudinally, this study introduces a pre-pubertal standard for the assessment of pre-pubertal height for children with late onset of puberty. By plotting the height values of a child in a chart containing pre-pubertal reference values, the onset of the pubertal growth spurt can be identified by a change in the pre-pubertal height standard deviation score values of 0.3 standard deviations or more over a period of 1 year. Once the pubertal onset is established, a highly accurate final height prediction method can be applied to the data, as described in this article, in which height and age at pubertal onset are the only two measures required. The r² value of the prediction model was over 0.80 for both sexes. Finally, a method for assessing total pubertal height gain is presented. The method adjusts for the timing of puberty and is based on the height and age at pubertal onset, plus the observed final height.

The purpose of this study was to assess the association of IGF-I and birth size by studying small for gestational age (SGA) subphenotypes and undertaking more detailed analysis of IGF-I genetic markers. SGA subjects from Haguenau, France (n = 113), and Gothenburg, Sweden (n = 174), were studied. The Swedish subjects were subphenotyped according to postnatal growth (114 short SGA and 60 SGA catch-up). IGF-I dinucleotide repeat and single nucleotide polymorphism (SNP) markers were studied, and haplotypes were generated in the Swedish short SGA group by identity of state. Association analysis was undertaken using the Monte Carlo method of association analysis of multiallelic markers for dinucleotide repeat markers, by exact chi(2) analysis for SNPs and by ANOVA for serum IGF-I levels. IGF-I genotype was associated with the SGA phenotype, in particular with symmetrical SGA and low birth weight, and with IGF-I levels in SGA subjects. Association with postnatal growth was different in the two populations, which may reflect the power of the smaller subphenotype groups. Haplotype analysis in the Swedish short SGA subjects showed that the region of association lay between the promoter and intron 2 of the IGF-I gene. These studies validate the association of the IGF-I gene with birth size and refine the region of association in Swedish short SGA subjects.

To facilitate the diagnosis of GH deficiency and monitor GH therapy, we constructed two reference models to allow comparison of serum IGF binding protein (IGFBP)-3 concentrations and IGF-I to IGFBP-3 ratios among children throughout childhood and adolescence. This report presents equations for determining the sd score of IGFBP-3 and IGF-I to IGFBP-3 measurements for individual patients. The data set contains serum values from 468 healthy children and adolescents (232 males, 236 females; ages 1.1-18.3 yr) whose height, weight, and body mass index were within +/- 3 sd of means. Puberty was classified according to breast development (B) and testicular volume into pre-, early, mid-, and late puberty. The values of IGFBP-3 and IGF-I to IGFBP-3 ratios were log transformed, and multiple linear regression analysis was used to identify models for converting serum concentrations into sd scores. The models include the variables of age, gender, and puberty and take into account the interactions among these variables. The best linear models explain 42% of the variation in serum IGFBP-3 concentrations and 50% of the variation in serum IGF-I to IGFBP-3 concentrations. The relationship between age and log(IGFBP-3) was positive for boys in pre-, early, and midpuberty. In late puberty, values were higher than earlier in puberty, and there was a negative relationship with age. For girls the relationship between age and log(IGFBP-3) also was positive in pre- and early puberty, with larger effect for girls older than 8 yr. Values for girls in midpuberty were relatively constant, and in late puberty values were higher than earlier in puberty, and there was a negative relationship with age. The relationship between age and log(IGF-I to IGFBP-3 ratio) was positive for boys in pre-, early, and early midpuberty (volume = 9-14 ml). In late midpuberty (volume = 15-19 ml), the relationship between age and IGF-I to IGFBP-3 ratio was negative. In late puberty, values were relatively constant and higher than earlier in puberty. For girls in prepuberty, the relationship with age was positive, with a larger effect in girls older than 8 yr. In early puberty, the girls' values were relatively constant. In early midpuberty (B = 3), log(IGF-I to IGFBP-3 ratio) values were higher for girls than boys of the same age. In late midpuberty (B = 4), the relationship with age was negative, and in late puberty values were relatively constant and higher than earlier in puberty.