Timing of adiposity rebound in children with congenital hypothyroidism diagnosed by newborn screening and treated with Levothyroxine

Background: Children with congenital hypothyroidism (CH) are at increased risk of developing childhood obesity. Moreover, an adiposity rebound (AR) that occur early is strongly linked with future obesity. The aims of our study were to explore the timing of AR, to identify factors affecting AR and correlation between age and body mass index (BMI) at AR and BMI at eight years of age in children with CH. Methods: A retrospective, observational study was conducted on Caucasian children with CH. For each child, BMI growth curve was constructed, AR was identified and compared with the Italian national and regional references. Results: Sixty-nine patients (44 females) were recruited. The age at AR was 3.4 ± 1.2 vs. 4.5 years of the comparison population (p < 0.001) in females and 3.4 ± 1.4 vs. 5.0 years of the comparison population (p < 0.001) in males with CH. Age at AR showed a significant negative correlation with BMI at 8 years (r = − 0.274, p < 0.039). BMI at AR and BMI at 8 years of age correlated positively (r = 0.460, p < 0.001). The prevalence of obesity/overweight at 8 years of age was 30%. BMI at 8 years of age was 22.4 ± 1.8 kg/m2 in overweight/obese subgroup and 16.9 ± 1.8 kg/m2 in normal BMI subgroup (P 0.001). Conclusion: Children with CH showed earlier AR compared to Italian national references. The higher risk of obesity in patients with early AR is supported by the association between age, BMI at AR, and BMI at eight years.