DNA-based diagnosis of thyroid hormone resistance syndrome: A novel THRB mutation associated with mild resistance to thyroid hormone

Thyroid hormones govern a wide range of metabolic processes in the body via thyroid hormone receptors (TR). We report a patient with mild resistance to thyroid hormone who was initially misdiagnosed and treated as having thyrotoxicosis. We used direct DNA sequencing of the THRB gene. We identified a novel missense mutation, I276L, located in exon 8 of the gene. The mutation is located in cluster 3 of the ligand-binding domain, a protein domain associated with resistance to thyroid hormone. DNA-based diagnosis of thyroid hormone resistance syndrome is simple, reliable, and economical compared to traditional biochemical tests. Once the mutation is identified, targeted screening for the whole family can be performed and the unnecessary use of anti-thyroid drugs or thyroidectomy can be avoided.