Thyroid peroxidase gene variants and susceptibility to congenital hypothyroidism and autoimmune thyroid disease among Egyptian pediatric cohort

Background: Pediatric thyroid disorders arise from com plex interactions among genetic susceptibility, immune dysregulation, and metabolic factors that influence their onset and severity.Purpose: This study aimed to evaluate the clinical, bio chemical, micronutrient, and genetic determinants of thyroid dysfunction in children with particular emphasis on the thyroid peroxidase (TPO) Arg 386 His and Thr 725 Pro polymorphisms.Methods: This casecontrol study enrolled 150 Egyptian children aged 2-15 years, including 50 with congenital hypothyroidism (CH), 50 with autoimmune thyroiditis (AIT), and 50 controls.The participants underwent clini cal assessments, routine laboratory investigations, thyro id function tests, and tests for selenium, copper, and thy roid autoantibodies (Tg Abs and TPO Abs).Following genomic DNA extraction from peripheral blood, the TPO gene polymorphisms (Arg 386 His and Thr 725 Pro) were analyzed using polymerase chain reactionrestriction fragment length polymorphism.Results: Children with thyroid disorders exhibit a high er prevalence of anemia and significantly lower ferritin levels.Profound micronutrient disturbances were evi dent and characterized by severe selenium deficiency and elevated copper concentrations.The genetic analy sis demonstrated a strong association between the TPO exon8 Arg 386 His polymorphism and pediatric thyroid disorders.The His allele and Hiscontaining genotypes were significantly more frequent among cases, particul arly in children with CH.A genotypephenotype correla tion revealed that the histidine/histidine (His/His) geno type was consistently associated with the highest serumthyroidstimulating hormone levels in both CH and AIT, suggesting greater functional impairment of thyroid hormone synthesis.Distinct genetic patterns were ob served between disease subtypes, with a predominance of the His allele in CH and the Arg allele in AIT.No variation was detected in the Thr725Pro polymorphism, and all participants exhibited the Thr/Thr genotype.Conclusion: These findings support a multifactorial model of pediatric thyroid disease, with the TPO Arg 386 His variant, particularly the His/His genotype, emerging as a key genetic contributor to disease susceptibility and severity.