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.TreatmentTreatment options for patients with MCT8 gene mutations are currently limited. Supportive measures include the use of braces to prevent malposition contractures that might ultimately require orthopedic surgery. Diet should be adjusted to prevent aspiration. Dystonia might be improved with medications such as anticholinergics, l-DOPA, carbamazepine, and lioresol. Drooling can be improved with glycopyrolate or scopolamine. Seizures should be treated with standard anticonvulsants. When refractory, a ketogenic diet has been successful, as has been the administration of supraphysiologic doses of L-T4. Experience with such treatments is, however, limited to only a few cases.In several infants, detection of low T4 or elevated TSH by neonatal screening has led to treatment with L-T4. However, no improvement has been noted when used in physiological doses, presumably because of the impaired uptake of the hormone in MCT8-dependent tissues. Administration of T4 during pregnancy and the efficacy of several TH analogs that might bypass the molecular defect by using alternative transporters, have therapeutic potential that are being tested in Mct8-deficient mice.