What is the treatment for hypothyroidism in infants?

Treatment of Hypothyroidism in Infants

The treatment of choice for congenital hypothyroidism in infants is immediate initiation of levothyroxine at a dosage of 10-15 mcg/kg/day orally. 1

Diagnosis and Screening

• Newborn screening for congenital hypothyroidism is available throughout the United States and is essential for early detection 1
• Diagnosis is based on:
  • Elevated TSH levels
  • Low free T4 or total T4 levels
  • Clinical symptoms may not be evident in newborns, making screening crucial

Treatment Protocol

Initial Management

1. Initiate treatment immediately upon diagnosis - Treatment in the first several weeks of life can result in nearly normal intelligence and growth 1, 2
2. Dosage:
   • Initial dose: 10-15 mcg/kg/day orally 1
   • For full-term infants: 25-50 micrograms/day 3
   • Goal is to rapidly normalize thyroid hormone levels

Monitoring and Dose Adjustment

• Monitor serum T4 and TSH levels:
  • Maintain total T4 or free T4 in the upper half of the reference range during the first 3 years of life 2
  • TSH should decrease as rapidly as possible below 20 microU/ml and then remain within normal range 3
• Follow-up testing:
  • First follow-up within 2 weeks of starting therapy
  • Frequent evaluations during the first 3 years of life 2

Special Considerations

• Preterm and very low birth weight infants:

  • May have delayed TSH elevation 4
  • Consider retesting TSH and free T4 even with initially normal newborn screening results 4
  • Small for gestational age infants are at higher risk for requiring thyroid hormone treatment 4

• Monitoring for adverse effects:

  • Closely monitor infants during the first 2 weeks of levothyroxine therapy for cardiac overload and arrhythmias 5
  • Some clinicians suggest lower initial doses (5.3-9.2 mcg/kg/day) to prevent iatrogenic hyperthyroidism 6

Expected Outcomes

• With early and adequate treatment, cognitive development can be normalized 2
• Excellent neuropsychointellectual prognosis when therapy and psychosocial environment are adequate 3
• IQ may be somewhat lower despite appropriate therapy in cases of severe prenatal hypothyroidism 3

Common Pitfalls to Avoid

1. Delayed treatment - Treatment must begin within the first 2 weeks of life to prevent neurodevelopmental impairment 2
2. Inadequate dosing - Insufficient therapy can lead to persistent hyperthyrotropinemia and poor outcomes 3
3. Overreliance on newborn screening - Normal newborn screening does not rule out hypothyroidism; clinical judgment remains essential 2
4. Poor compliance - Persistent elevated TSH despite normal T4 may indicate poor compliance with medication 3
5. Failure to recognize transient hypothyroidism - Some cases may be transient, particularly in preterm infants or those with iodine exposure 3

Long-term Management

• Levothyroxine therapy is generally continued for life in patients with permanent congenital hypothyroidism 5
• Regular monitoring of thyroid function tests to ensure optimal dosing
• Ongoing developmental assessment to identify and address any delays

Remember that early diagnosis and prompt treatment are crucial for preventing the adverse effects of congenital hypothyroidism on cognitive development and physical growth.