An Exploratory Cross-Sectional Study on Thyroid Hormone Reference Intervals in Children With Down syndrome

Accurate evaluation of thyroid dysfunction in children with Down syndrome is challenging because of the lack of age-specific reference intervals in these individuals. This study aimed to establish age-specific reference intervals for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels in children with Down syndrome.

A retrospective cross-sectional study was conducted on children with Down syndrome, aged 6 months to 15 years, who visited the Osaka Women's and Children's Hospital between April 2019 and March 2020. Subjects who had used medications that influenced thyroid function or who lacked thyroid hormone data were excluded from the study. The final analysis included 301 subjects. Serum TSH and FT4 levels were measured, and reference intervals were calculated using nonparametric methods.

The reference intervals for TSH in children with Down syndrome were 2.03-14.22, 1.79-12.98, 1.26-10.24, and 0.58-10.11 mIU/L in infants, toddlers, school children, and adolescents, respectively, which were higher than those observed in the general paediatric population. The reference intervals for FT4 were 13.57-26.42, 13.20-22.70, 13.15-22.36, and 11.97-24.77 pmol/L, respectively, which were comparable to those of the general paediatric population. Multivariate regression analyses revealed a significant inverse association between age and the levels of TSH and FT4 (p < 0.01).

We provide evidence for age-specific reference intervals for TSH and FT4 levels in children with Down syndrome, which may help clinicians accurately evaluate thyroid hormone status.