Congenital hypothyroidism (CH), due to dyshormonogenesis, occurs due to defective thyroid hormone biosynthesis in a structurally normal gland, and causes include mutations in the reduced form of NAD phosphate (NADPH)-oxidase DUOX2, which generates the hydrogen peroxide (H2O2) required for the organification of iodide. The gene discussed is DUOX2; the disease is congenital hypothyroidism.