Anti-thyroid peroxidase antibodies in autism spectrum disorder: a marker of subclinical autoimmune activity in children

Objectives This study aimed to evaluate anti-thyroid peroxidase (anti-TPO) antibodies as a potential biomarker of autoimmune susceptibility in autism spectrum disorder (ASD).Methods We enrolled 81 children aged 2–7 years with ASD and 60 typically developing controls. All participants were evaluated using the Schedule for Affective Disorders and Schizophrenia for School-Age Children – Present and Lifetime Version (K-SADS-PL), the Childhood Autism Rating Scale (CARS), and an age-appropriate developmental or intelligence assessment. Fasting serum samples were analyzed for anti-TPO, thyroid-stimulating hormone (TSH), and free thyroxine (fT4) levels using the electrochemiluminescence method.Results Anti-TPO levels were significantly higher in ASD than in controls (p < 0.001), while TSH and fT4 were comparable; receiver operating characteristic analysis indicated moderate discriminative ability (AUC = 0.718). Anti-TPO levels were not correlated with autism symptom severity. In multivariable models, elevated anti-TPO levels, advanced paternal age, and a family history of psychiatric disorders were independently associated with the presence of ASD.Conclusions These findings suggest that children with ASD may exhibit subtle subclinical autoimmune activation, even within normal anti-TPO ranges. Anti-TPO antibodies may therefore serve as a biomarker of autoimmune susceptibility in autism. Larger, longitudinal studies are warranted to clarify their prognostic value and potential role in early risk stratification.