What is the treatment for hypothyroidism (underactive thyroid) in children?

Treatment of Hypothyroidism in Children

Levothyroxine replacement therapy is the standard treatment for hypothyroidism in children, with dosing based on age, weight, and severity of the condition. 1, 2

Diagnosis and Evaluation

Before initiating treatment, proper diagnosis is essential:

• Measure both TSH and free T4 levels for accurate diagnosis
• Clinical manifestations may include:
  • Growth failure
  • Delayed bone age
  • Delayed puberty
  • Constipation
  • Fatigue
  • Cold intolerance
  • Dry skin
  • Prolonged jaundice in infants
  • Large posterior fontanelle
  • Large tongue
  • Umbilical hernia 3

Levothyroxine Dosing Guidelines

Dosing by Age Group

• Newborns to 3 months:

  • Standard starting dose: 10-15 mcg/kg/day 2, 3
  • For infants at risk for cardiac failure: Start at lower dose and increase every 4-6 weeks based on clinical and laboratory response 2

• Infants and children:

  • Adjust dose based on weight and clinical response
  • For children at risk for hyperactivity: Start at one-fourth the recommended dose and increase weekly by one-fourth until full replacement dose is reached 2

Treatment Goals

• Maintain TSH < 5 mIU/L 4
• Keep free T4 or total T4 in the upper half of the age-specific reference range 4, 3
• Eliminate all symptoms and signs of hypothyroidism 4
• Ensure normal growth and development 4

Monitoring Protocol

• Initial period:

  • Check TSH and free T4 at 2 and 4 weeks after treatment initiation
  • Recheck 2 weeks after any dosage change 2

• Maintenance period:

  • Monitor every 3-12 months after dosage stabilization until growth is completed 2
  • More frequent monitoring for poor compliance or abnormal values

• Clinical evaluation:

  • Regular assessment of development
  • Mental and physical growth
  • Bone maturation 2

Special Considerations

Congenital Hypothyroidism

• Begin treatment as soon as possible, preferably within the first 2 weeks of life to optimize neurocognitive outcomes 4, 3
• Early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood 3

Children with Chronic Kidney Disease

• Correct metabolic acidosis (serum bicarbonate levels ≥22 mEq/l) before initiating growth hormone therapy 5
• Measure thyroid hormone levels, including serum TSH and free T3, before growth hormone therapy 5

Children with Cancer History

• Higher risk of hypothyroidism in children who received neck radiation or total body irradiation 5
• Most common presentation is within first 5 years following radiation, but can occur up to 20+ years later 5
• Regular screening with TSH and free T4 is recommended, especially during periods of rapid growth 5

Potential Complications of Treatment

• Overtreatment risks:

  • Craniosynostosis
  • Acceleration of bone age
  • Cardiac overload in infants (first 2 weeks of therapy) 2

• Undertreatment risks:

  • Adverse effects on cognitive development
  • Impaired linear growth 2
  • Permanent nervous system damage, especially in infants 6

Pitfalls to Avoid

1. Delaying treatment in congenital hypothyroidism - can lead to irreversible neurodevelopmental damage
2. Inadequate monitoring during periods of rapid growth when dose adjustments may be needed
3. Failure to recognize hypothyroidism despite normal newborn screening results when clinical symptoms are present 3
4. Not adjusting dosage as the child grows, leading to undertreatment

Remember that thyroid hormones are critical for early neurocognitive development as well as growth throughout childhood. Prompt recognition and adequate treatment of hypothyroidism is crucial to optimize physical and neurodevelopmental outcomes 4.