Congenital Primary Hypothyroidism with the Homozygous Nonsense Mutation P.K1374* in the Thyroglobulin Gene and a Normal-sized Thyroid Gland on Levothyroxine Replacement

Thyroglobulin (TG) gene mutations cause thyroid dyshormonogenesis, which is typically associated with a congenital goiter. We herein report the case of a 64-year-old man with congenital primary hypothyroidism who had a normal-sized thyroid gland on levothyroxine replacement. He had short stature (−3.1 standard deviations) and mild intellectual impairment. Thyroid autoantibodies were all negative, and the serum TG levels were undetectable. Eventually, he was found to have the novel homozygous nonsense mutation p.K1374* in the TG gene. The possibility of TG mutation should be considered for patients with congenital primary hypothyroidism and a very low serum TG level, regardless of the thyroid size.