Retrospective analysis and literature review of four cases of thyroid hormone resistance syndrome caused by THRB gene mutation

Background: To summarize the clinical characteristics, genetics and follow-up data of four children with thyroid hormone resistance (RTH) syndrome and review the related literatures.Methods: The clinical data of the four children diagnosed with RTH syndrome in our hospital from 2018 to 2020 were retrospectively analyzed. Next-generation sequencing of the candidate genes related to thyroid diseases was performed using the blood collected from all the children and their parents who signed an informed consent. Then, relevant cases were retrieved on medical literature databases for analysis and summary.Results: Among the four cases, three cases of goiter; two cases of tachycardia, palpitations, personality change, hyperactivity, weight loss; one case of academic performance decline, and no hearing and vision loss were observed. Laboratory thyroid function tests indicated a mild increase in free triiodothyronine and with or without increased free thyroxine levels. Thyroid-stimulating hormone (TSH) levels were normal or slightly elevated, but thyrotropin receptor autoantibodies were negative. Octreotide inhibition test showed that the TSH levels of all the children decreased by more than 50% compared with the basal value (the genes of four cases were positive). However, magnetic resonance imaging of the pituitary gland showed no abnormalities. Related gene detection in the children and their families showed that four cases had THRB mutations: two proband mutations were from their fathers, and two cases had de novo mutations.Conclusions: The clinical manifestations of pediatric RTH syndrome vary, and the diagnosis mainly depends on thyroid function tests. Heterozygous mutations in THRB are overall rare, even if with the advanced development of next-generation sequencing, not all the children with RTH syndrome have mutations. Furthermore, octreotide inhibition tests cannot be used as a diagnostic criterion to distinguish RTH syndrome from pituitary tumors in children.