Practice points•Goiter, attention d

Practice points•Goiter, attention deficit hyperactivity disorder and tachycardia are the most common reasons leading to the testing and – ultimately – the diagnosis of RTH.•Genetic analysis of subjects suspected of having RTH provides a short cut to diagnosis.•Failure to identify a TRβ gene mutation in genomic DNA from the lymphocytes of subjects presenting the RTH phenotype, could be due to mosaicism in a de-novo mutation or to a yet unidentified etiology of the syndrome (non-TR RTH).•Ablative treatment in RTH complicates the follow up and outcome, as adjustment of TH replacement is not easy.