Abstract: Objective To study mutations of thyroid hormone receptor β gene (TRβ) and clinical characteristics of a patient with resistance to thyroid hormone (RTH) associated with Hashimoto's thyroiditis (HT). Methods clinical manifestations were observed in a 7-year-old boy with RTH. Meantime, genomic DNA was extracted from peripheral blood of the patient and his parents. exons 5～10 of TRβ gene were amplified by PCR and sequenced directly. Results A heterozygote point mutation in exon 10 of TRβ was identified in the patient, which is a A to T transition in nucleotide 1403（c. 1304 A > T）, resulting in His to Leu ( CAT→CTT) substituted at codon 435 ( H435L). No mutation was identified in the patient's parents. HT occurred in the patient during following-up. Conclusion H435L mutation in exon 10 of TRβ gene leads to resistance to thyroid hormone. Meanwhile, consistent RTH might lead to HT.

Key words: thyroid hormone receptor β gene, resistance to thyroid hormone, Hashimoto’s thyroiditis