A A consanguineous pedigree showing two affected members (IV: 2 and IV: 5) in the fourth generation with congenital hypothyroidism. Affected individuals in the pedigree are shown with shaded symbols, and unaffected individuals are indicated with open symbols. Double lines indicate a consanguineous union. B Sequence chromatogram showing the missense TPO variant. The red arrow indicates the site of the identified variant in this study. Affected individuals (IV: 2 and IV: 5) are homozygous, parents (III: 1 and III: 2) and two normal brothers (IV: 1 and IV: 4) are heterozygous, and two siblings (IV: 3 and IV: 6) are homozygous normal for the identified variant. C Schematic representation of TPO protein and its domains; arrow indicates the location of the mutation identified in the present study. D Conservation of p.Tyr772 across several species.