Objective:Thyroid dyshormonogenesis is a genetically heterogeneous group ofinherited disorders in the enzymatic cascade of thyroid hormone synthesisthat result in CH gene mutations are one of the most common causes ofthyroid dyshormogenesis. The aim of this study was to determine thenature and frequency of TPO gene mutations in patients with CH, as thesepatients are liable to develop multinodular goiter and follicular carcinoma,thus they require regular follow up to detect them at an early stage.Subjects and Methods :Thirty three patients with permanent CH and goitre participated inthis study. Thyroglobulin was measured by Immulite, mutational analysis ofthe TPO gene was done using restriction fragment length polymorphismanalysis (RFLP).Results:TPO gene mutations were identified in 21.4% of participants, namelyGGCC duplication insertion at exon 8. Allele frequency n was 17.9%.Conclusions:The results showed a high prevalence of TPO gene mutations inpatients with thyroid dyshormongenesis similar to the published studies.