Treatment of Congenital Hypothyroidism
Levothyroxine (L-thyroxine) therapy should be initiated as soon as possible after diagnosis, preferably within the first 2 weeks of life, at a dose of 10-15 mcg/kg/day to optimize neurocognitive outcomes in infants with congenital hypothyroidism. 1
Diagnosis and Initial Assessment
- Congenital hypothyroidism is the most common endocrine disorder in neonates
- Most infants (>95%) have few or no clinical manifestations at birth 2
- Diagnosis is primarily made through newborn screening programs
- Clinical signs that may suggest hypothyroidism include:
- Large posterior fontanelle
- Large tongue
- Umbilical hernia
- Prolonged jaundice
- Constipation
- Lethargy
- Hypothermia 1
Treatment Protocol
Initial Therapy
- Start levothyroxine immediately upon confirmation of diagnosis
- Do not delay treatment for additional diagnostic tests (ultrasonography, scintigraphy, etc.) 3
- Recommended initial dosage: 10-15 mcg/kg/day 1
- For severe hypothyroidism (TSH >100 μIU/L): 10-11.9 mcg/kg/day
- For moderate hypothyroidism (TSH <100 μIU/L): 8-10 mcg/kg/day 4
Treatment Goals
- Maintain serum TSH <5 mIU/L
- Keep free T4 or total T4 in the upper half of age-specific reference range 2
- Normalize TSH within 4 weeks of starting treatment 5
- Eliminate all symptoms and signs of hypothyroidism
Monitoring
- Check thyroid function tests frequently during the first year of life
- Adjust dosage based on laboratory results and clinical response
- Monitor for overtreatment (T4>16 μg/dL/free T4>2.3 ng/dL±TSH <0.5 μIU/L) 4
- Watch for signs of undertreatment (TSH>6 μIU/L) 4
Special Considerations
Pregnancy
- Untreated maternal hypothyroidism during pregnancy increases risk of:
- Spontaneous abortion
- Gestational hypertension
- Pre-eclampsia
- Stillbirth
- Premature delivery 6
- Pregnancy may increase levothyroxine requirements
- Monitor TSH levels and adjust dosage during pregnancy 6
Breastfeeding
- Levothyroxine is present in human milk but no adverse effects on breastfed infants have been reported
- Adequate levothyroxine treatment may normalize milk production in hypothyroid mothers 6
Long-term Outcomes
Research shows that when treatment is started within the first 2 weeks of life, mental retardation can be prevented in >90% of children with congenital hypothyroidism 3. Early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood 1.
Pitfalls to Avoid
- Delaying treatment while awaiting additional diagnostic tests
- Underdosing levothyroxine, especially in severe cases
- Inconsistent follow-up and monitoring
- Ignoring hypothyroidism despite clinical symptoms when screening results are normal 1
- Excessive dosing (>12 μg/kg/day) which may lead to overtreatment 4
Early diagnosis and prompt treatment with appropriate levothyroxine dosing are crucial for optimal neurocognitive development in children with congenital hypothyroidism.