title: Children with hyperthyroidism younger than age 7 require higher mg/kg doses of methimazole to normalize free T4 compared to older children.
abstract: BACKGROUND
  Hyperthyroidism is much less common in children <7 years vs. older children and less well studied. It was our impression that the youngest patients needed a higher weight-based dose of methimazole (MMI) to achieve euthyroidism.
  
  
  OBJECTIVE
  To compare the mean MMI dose needed to normalize free T4 in younger (<7 years) vs. older children and the time taken to normalize free T4.
  
  
  METHODS
  Based on chart review (2004-2012), patients were divided into groups based on age at diagnosis: <7 years (n=13), 7-12 years (n=30) and >12 years (n=40). Follow-up visits were reviewed until free T4 normalized.
  
  
  RESULTS
  The mean dose of MMI (mg/kg/day) needed to normalize free T4 was 0.71 (±0.29) in the <7 group, significantly higher vs. the two older groups: 0.50 (±0.22) and 0.44 (±0.24). Months taken to achieve a euthyroid state was significantly longer in children <7 (6.23±3.91) vs. the older groups (3.10±2.12 and 3.18±2.86 months).
  
  
  CONCLUSIONS
  Hyperthyroid children diagnosed before age 7 required higher initial doses of MMI and took a longer time to become euthyroid than older patients. Clinicians should consider starting with higher weight-based MMI doses when treating younger patients to more rapidly normalize free T4.
authors.forename: Diana
authors.initials: D
authors.lastname: Stafford
authors.forename: Priya
authors.initials: P
authors.lastname: Vaidyanathan
authors.forename: Paul
authors.initials: P
authors.lastname: Kaplowitz
mesh_terms: D000293:Adolescent; D000367:Age Factors; D013956:Antithyroid Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000188:drug therapy*; D008297:Male; D008713:Methimazole / Q000008:administration & dosage* / Q000627:therapeutic use; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood*; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D008713:Methimazole; D013974:Thyroxine