Changes in thyroid volume and insulin-like growth factor 1 in pre- and post-pubertal obese children.

Abstract

There is a mutual dynamic interaction between thyroid volume (TV), insulin-like growth factor-1 (IGF-1), and body mass index (BMI). These covariates undergo a change with the transition into puberty. The heterogeneity of the variates and study populations complicate the evaluation of the role of pure pubertal effect. The purpose of this study was to investigate the effect of puberty on IGF-1 and TV in a predetermined homogenous population such as obese children. Three hundred and eighty children (202 girls and 178 boys) aged between 6 and 18 were enrolled in this prospective study. The children were assigned to two groups according to their pubertal status, i.e., prepubertal (n = 169) and postpubertal (n = 211). According to age and sex, the obese group (n = 222) was made up of children at and above the 95th percentile, and the control group (n = 158) of children under the 85th percentile. The following parameters were evaluated in all children: BMI, pubertal status, TV, and serum IGF-1, IGFBP-3, and IGF-1:IGFBP-3 molar ratio. In comparison to the prepubertal obese group, the obese group at Tanner stage 2 had a larger mean TV (P = 0.008) and higher IGF-1 level (P = 0.033). There was a positive correlation between IGF-1 and TV both in the prepubertal and pubertal group (r169= 0.369, P = 0.001; r211= 0.316, P = 0.004, respectively), whereas there was no correlation between IGF-1 and BMI (r169= 0.99, P = 0.092; r211= 0.094, P = 0.088, respectively). This study showed that the TV and serum IGF-1 levels were increased in obese children in the early stage of puberty and that there was a positive correlation between these two variables in all children, which shows the specific effect of the early stage of puberty on the increase in TV and IGF-1 levels and suggests that increased TV is associated with the increase in IGF-1 levels in a homogenous group such as obese children.