Adiposity rebound and body mass index in Japanese patients with congenital hypothyroidism

The long-term prognosis of congenital hypothyroidism (CH) has become apparent since the introduction of newborn screening programs; however, the risk of obesity in patients with CH remains unclear. Early adiposity rebound (AR) is one of the predictors of obesity in adults. This study evaluated AR and the adolescent body mass index (BMI) in Japanese patients with CH. We longitudinally collected anthropometric measurements from 288 patients aged 1-10 yr and plotted their BMI curves to determine the age at onset of AR. We also evaluated the effects of thyroid function, presence of distal femoral epiphysis (DFE) ossification, and disease type on AR age and adolescent BMI. The mean AR ages were determined to be 5.5 ± 1.4 yr in boys and 5.9 ± 1.5 yr in girls. There were no significant differences in AR age or adolescent BMI according to thyroid-stimulating hormone or free T4 levels before treatment initiation or according to disease type. However, at the last visit, more than half of the boys without DFE ossification had higher BMI SD scores than those with DFE ossification. These findings raise the possibility that severe prolonged fetal hypothyroidism may have a lasting influence after birth despite early treatment initiation.