Mutations in the DUOX2 gene, whose protein function is to generate hydrogen peroxidase required for thyroid hormone synthesis in the follicular cells, are involved in the development of congenital hypothyroidism, and are typically found in the N-terminal extra cellular peroxidase-like domain and in the EF hand domains, where they compromise the enzymatic activity of the protein. The gene discussed is DUOX2; the disease is congenital hypothyroidism.