Background: 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.
Objective: 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.
Subjects and methods: 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.
Results: 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).
Conclusion: 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.
Keywords: Childhood obesity; insulin-like growth factor-1; puberty; thyroid volume.