Transient Congenital Hypothyroidism Caused by Biallelic Mutations of the Dual Oxidase 2 Gene in Japanese Patients Detected by a Neonatal Screening Program

Abstract

Context: Mutations in dual oxidase (DUOX2) have been proposed as a cause of congenital hypothyroidism. Previous reports suggest that biallelic mutations of DUOX2 cause permanent congenital hypothyroidism and that monoallelic mutations cause transient congenital hypothyroidism. Objective: To clarify the inheritance of hypothyroidism, we looked at the DUOX2 gene in patients with transient congenital hypothyroidism. Design: DUOX2, thyroid peroxidase, Na+/I− symporter and dual oxidase maturation factor 2 genes were analyzed in eight patients with transient congenital hypothyroidism, using the PCR-amplified direct sequencing method. Patients: The eight patients were found by a neonatal screening program. Six of these patients belonged to two independent families; the other two were unrelated. Their serum TSH values varied from 24.8–233.0 mU/liter. Six of the eight patients had a low serum freeT4 level (0.19–0.84 ng/dl). Seven of the eight patients were treated with thyroid hormone replacement therapy, which ceased to be necessary by 9 yr of age. Results: Eight novel mutations were detected in the DUOX2 gene. Four patients in one family were compound heterozygous for p.L479SfsX2 and p.K628RfsX10. Two patients in a second family were compound heterozygous for p.K530X and p.[E876K;L1067S]. The two remaining unrelated patients were also compound heterozygous, for p.H678R/p.L1067S and p.A649E/p.R885Q, respectively. Conclusion: All eight patients had biallelic mutations in the DUOX2 gene. We find that loss of DUOX2 activity results in transient congenital hypothyroidism and that transient congenital hypothyroidism caused by DUOX2 mutations is inherited as an autosomal recessive trait.