A Case of Resistance to Thyroid Hormone (RTH) with a Negative Family History with Diagnosis Based on Persistent Palpitations.

Approximately 140 different mutations of thyroid hormone receptor β (TRβ) have been identified in resistance to thyroid hormone (RTH). We report herein a middle-aged man with a negative family history who was diagnosed with RTH based on persistent palpitations. Genetic analysis showed a TRβ mutation causing the substitution of alanine for proline 453 (P453A) in exon 10. Since treatment of RTH is different from that of Graves' disease and thyroid stimulating hormone-producing adenoma (TSHoma), a genetic analysis should be performed even in patients who have a negative family history of RTH and who are free of TSHoma when they present with persistent inappropriate secretion of thyroid stimulating hormone (SITSH).