title: Treatment with methimazole in a 3-year-old male with thyroid hormone resistance.
abstract: BACKGROUND
  Thyroid hormone resistance syndromes are disorders in which there is decreased end-organ responsiveness to thyroid hormone. Patients typically present with elevated levels of thyroxine and triiodothyronine with a normal or increased serum thyroid-stimulating hormone concentration. Clinical features are variable, and there are no guidelines regarding treatment.
  
  
  METHODS
  The patient was noted to have tachycardia at 6 months of age. He had persistently elevated free thyroxine and normal/mildly elevated thyroid-stimulating hormone for the first 2 years of life. At age 2 years, he was noted to have sinus tachycardia, a mildly enlarged thyroid, hyperactive behavior, subtle developmental delay, and poor weight gain. The patient has a previously described de novo mutation in the thyroid hormone receptor-β gene.
  
  
  RESULTS
  He was started on methimazole (0.3-0.5 mg/kg/day) at age 3 years to treat his symptoms. With medication, weight gain, sleep, behavior, and tachycardia improved. Linear growth has remained appropriate for age. Heart rate is in the upper normal range and his thyroid has become more enlarged.
  
  
  CONCLUSIONS
  Methimazole has improved thyrotoxic symptoms in a 3-year-old male with thyroid hormone resistance. The use of methimazole should be considered in certain patients.
authors.affiliation: Division of Endocrinology, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ont., Canada. s.lenihan.tsai@gmail.com
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Tsai
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ahmet
mesh_terms: D000367:Age Factors; D013956:Antithyroid Agents / Q000627:therapeutic use; D002675:Child, Preschool; D006801:Humans; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D013610:Tachycardia / Q000188:drug therapy / Q000209:etiology; D018382:Thyroid Hormone Resistance Syndrome / Q000150:complications / Q000188:drug therapy*; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D008713:Methimazole