Long-term effects of L-thyroxine therapy for congenital hypothyroidism

J Pediatr. 1995 Mar;126(3):380-6. doi: 10.1016/s0022-3476(95)70452-3.


Objective: To study the effects of initial and concurrent dose levels of L-thyroxine on ability and behavior in children with congenital hypothyroidism.

Methods: An existing database, involving a large cohort of children with congenital hypothyroidism detected by neonatal screening, was analyzed retrospectively. There were 94 children: 89 were assessed at age 7 years for intelligence and selective cognitive abilities, and 87 at age 8 years for behavior, achievement, and selective abilities.

Results: Subjects were stratified by median split into low and high starting dose groups. The high-dose group performed better on indexes of intelligence, verbal ability, and memory but had more behavior problems reflecting increased anxiety, social withdrawal, and poorer concentration. The dose of L-thyroxine at age 8 years was negatively correlated with memory task performance.

Conclusion: A higher starting dose of L-thyroxine is beneficial for subsequent intellectual outcome in children with congenital hypothyroidism but may be associated with internalizing behavior problems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Child Behavior Disorders / etiology*
  • Congenital Hypothyroidism*
  • Female
  • Humans
  • Hypothyroidism / drug therapy
  • Hypothyroidism / psychology
  • Infant
  • Infant, Newborn
  • Intelligence / drug effects*
  • Male
  • Prospective Studies
  • Psychological Tests
  • Thyroxine / administration & dosage*
  • Thyroxine / adverse effects
  • Thyroxine / therapeutic use


  • Thyroxine