A rare mutation in THRB gene of resistance to thyroid hormone: a case report of a Chinese pedigree

Learning points for cliniciansClinical manifestations of resistance to thyroid hormone syndrome (RTH) exhibit a wide range of variations.Here, we present a Chinese pedigree harboring a thyroid hormone receptor beta (THRB) gene mutation (c.1358C>T) with clinical evidence of thyrotoxicosis. Case PresentationThe proband, a 34-year-old male patient, was initially admitted to another hospital with goiter and symptoms of thyrotoxicosis such as palpitations, irritability, insatiable appetite and heat intolerance since the age of 10.Hormonal assessment revealed elevated triiodothyronine(T3) and thyroxine (T4) levels, contrasting with non-suppressed thyroid-stimulating hormone(TSH).Administered antithyroid therapy for 5 months, the patient's thyroid hormone(TH) levels slightly dropped while his TSH levels rose dramatically above the upper normal limit.The proposita was then treated with propranolol to control his heart beats and tremor.To differentiate from TSH-secreting adenomas(TSHoma), the High dose dexamethasone test was performed and it showed a TSH inhibition rate of approximately 65.78%.Afterwards, a 42% TSH inhibition rate was identified during T3 suppression test.Moreover, thyroid ultrasonography revealed a diffuse enlargement.Pituitary enhanced MRI showed decreased enhancement on the right side with an unclear margin.Somatostatin receptor imaging, however, showed no significant findings.Perimetry showed a right temporal scotoma and a left nasal scotoma.No tumor tissues were found during the endonasal exploratory surgery.The patient was then transferred to our hospital and we conducted Sanger sequencing on the patient and his 18 other family members (Figure 1).