Thyroid function in children with attention-deficit/hyperactivity disorder and specific learning disorder: a retrospective comparative study.

BACKGROUND/AIM: This study analyzes thyroid function parameters (free T3, free T4, TSH) in children with attention-deficit/hyperactivity disorder (ADHD), ADHD with specific learning disorder, and healthy controls, to determine whether subtle thyroid dysregulation contributes to the phenotypic heterogeneity of ADHD. MATERIALS AND METHODS: This retrospective, cross-sectional study included 135 children aged 6-18 years: 62 diagnosed with ADHD (38 isolated ADHD and 24 ADHD+SLD) and 73 healthy controls. Demographic, anthropometric, and thyroid function data (free T3, free T4, TSH) were extracted from medical records. Group comparisons were conducted using independent samples t-tests, ANOVA, and ANCOVA adjusted for age, sex, and treatment status. RESULTS: Children with ADHD exhibited higher free T3 (p = 0.003), lower free T4 (p = 0.020), and higher TSH (p = 0.048) levels than the controls. Subclinical hypothyroidism, isolated T3 elevation, and euthyroid Hashimoto thyroiditis were more prevalent in the ADHD group (p = 0.032). No significant thyroid parameter differences were observed between isolated ADHD and ADHD+SLD. The direction of these endocrine differences persisted after covariate adjustment, although only free T3 remained statistically significant, suggesting subtle hypothalamic-pituitary-thyroid axis dysregulation in ADHD independent of stimulant treatment. CONCLUSION: Children with ADHD exhibit subtle alterations in thyroid function, characterized by higher T3 and TSH and lower T4 levels, which may reflect compensatory or metabolic imbalance rather than overt thyroid disease. These findings highlight the potential role of neuroendocrine modulation in the pathophysiology of ADHD.