In conclusion, this first systematic and comprehensive screening of 21 candidate genes in Chinese patients with CH showed that the most frequently mutated gene was DUOX2. Our result that 57/110 (51.82%) patients carried biallelic mutations in genes involved in thyroid hormone synthesis (DUOX2, TPO, TG, DUOXA1, TSHR or DUOXA2) suggests that in more than 50% of Chinese patients with CH, the disease is caused by thyroid dyshormonogenesis and is inherited in an autosomal recessive manner. The gene discussed is TPO; the disease is cyclic hematopoiesis.