What is the treatment approach for congenital hypothyroidism?

Treatment Approach for Congenital Hypothyroidism

Immediate treatment with levothyroxine at a dose of 10-15 mcg/kg/day should be initiated as soon as congenital hypothyroidism is diagnosed, ideally within the first two weeks of life to prevent neurocognitive impairment. 1

Diagnosis and Screening

• Congenital hypothyroidism is the most common endocrine disorder in neonates
• Newborn screening is essential and available throughout the United States 2
• More than 95% of infants with congenital hypothyroidism have few or no clinical manifestations at birth 3
• When clinical symptoms are present, they may include:
  • Large posterior fontanelle
  • Large tongue
  • Umbilical hernia
  • Prolonged jaundice
  • Constipation
  • Lethargy
  • Hypothermia 1

Initial Treatment

• Start levothyroxine immediately upon diagnosis - do not delay for additional diagnostic testing such as ultrasound or scintigraphy 4
• Initial dosage: 10-15 mcg/kg/day orally 1
• Treatment should begin within the first 2 weeks of life for optimal neurocognitive outcomes 4, 3
• Early treatment prevents mental retardation in >90% of children with congenital hypothyroidism 4

Treatment Goals and Monitoring

• Maintain serum TSH within normal range (ideally <5 mIU/L) 3
• Keep free T4 or total T4 within the upper half of age-specific reference range 3
• Monitor thyroid function closely:
  • Every 2-4 weeks during the first months of treatment
  • Every 1-3 months during the first year of life
  • Every 2-4 months during early childhood 3
• Dose adjustments should be made based on thyroid function tests

Long-term Considerations

• Children with congenital hypothyroidism typically require higher weight-based doses than adults with acquired hypothyroidism 5
• Treatment is generally continued for life in patients with permanent congenital hypothyroidism 6
• Close monitoring during the first 2 weeks of therapy for cardiac overload and arrhythmias 6
• The first 3 years of life are particularly critical for maintaining consistent euthyroidism for optimal neurodevelopment 1

Special Considerations

• Infants with congenital hypothyroidism may have a more sensitive response to initial thyroid hormone replacement depending on the etiology (dyshormonogenesis vs. thyroid dysgenesis) 7
• Controversy exists regarding optimal management of special populations, including preterm or low-birth-weight infants and infants with transient or mild congenital hypothyroidism 1

Potential Pitfalls

• Delayed treatment beyond the first few weeks of life significantly increases the risk of permanent neurocognitive impairment
• Inadequate dosing may result in suboptimal neurodevelopmental outcomes
• Overtreatment can lead to craniosynostosis and accelerated bone age
• Failure to recognize congenital hypothyroidism despite normal newborn screening results when clinical symptoms are present

Early diagnosis and prompt treatment with appropriate doses of levothyroxine are essential for preventing the adverse neurodevelopmental consequences of congenital hypothyroidism.