Down syndrome, caused by trisomy 21, is characterized by congenital abnormalities as well as mental retardation. From the neonatal stage through adolescence, patients with Down syndrome often have several complications. Thus, it is important to attain knowledge of the prevalence of these comorbidities in children with Down syndrome. We, therefore, evaluated the biochemical data, thyroid function, and anthropometric parameters, and analyzed the association among them in Japanese children and early adolescents with Down syndrome. There was no difference in the prevalence of obesity and overweight between boys and girls. The level of uric acid was higher in boys than in girls. Moreover, the prevalence of hyperuricemia was also higher in boys than in girls (approximately 32% and 10%, respectively). The prevalence of subclinical hypothyroidism in children with Down syndrome was approximately 20%, with no significant sex differences. The levels of uric acid and dehydroepiandrosterone-sulfate were positively associated with age, while the levels of thyroid-stimulating hormone and free thyroxine had a negative association with age. Overall, children with Down syndrome, exhibit a higher incidence of hyperuricemia. Therefore, uric acid levels, as well as thyroid function, from childhood to early adulthood should be monitored in this patient cohort.

Obesity is associated with health consequences, and thyroid dysfunction may be an adaption to the increased energy expenditure in obesity. With the rising prevalence of obesity in childhood, the prevalence of metabolic syndrome may also increase. In the current study, we have shown gender differences in the association of thyroid hormones with obesity, and attempted to elucidate the relationship between thyroid hormones and anthropometric parameters and biochemical data in obese Japanese children. We analyzed anthropometric measurements, blood pressure, body composition, thyroid hormones, and lipid profiles in 283 obese children. The association between thyroid hormones and several parameters differed by gender. The free T3 to free T4 ratio (fT3/fT4) in boys was negatively associated with the quantitative insulin sensitivity check index, whereas in girls, thyroid-stimulating hormone levels were positively correlated with levels of glucose, diastolic blood pressure, and non-high density lipoprotein-cholesterol, and fT3/fT4 was positively correlated with uric acid levels. FT3/fT4 in boys with metabolic syndrome was relatively higher than in those without metabolic syndrome. The cause of gender differences is unknown. Therefore, further studies with larger sample sizes and a long-term follow-up period are needed to address the influence of thyroid hormones on various parameters.