What to do next for a 7-day-old baby with elevated Thyroid-Stimulating Hormone (TSH) levels on newborn screening?

Management of Elevated TSH in a 7-Day-Old Newborn

For a 7-day-old baby with elevated TSH on newborn screening, immediate confirmatory venous thyroid function testing (TSH and free T4) should be performed, followed by prompt initiation of levothyroxine treatment if congenital hypothyroidism is confirmed. 1

Immediate Steps

1. Confirmatory Testing:

   • Obtain venous blood sample for confirmatory TSH and free T4 measurement 2, 1
   • Do not delay treatment while waiting for imaging studies 3

2. Diagnostic Criteria:

   • Venous confirmatory TSH >20 mIU/L before age 2 weeks indicates primary congenital hypothyroidism 3
   • Low T4 (<10 μg/dL) or free T4 (<1.17 ng/dL) with elevated TSH confirms the diagnosis 3

3. Treatment Initiation:

   • Start levothyroxine immediately at 10-15 μg/kg/day once diagnosis is confirmed 3
   • Do not delay treatment for imaging studies or other diagnostic procedures 3

Additional Diagnostic Evaluation

While treatment is being initiated, consider:

• Thyroid imaging: Schedule thyroid ultrasound and/or radionuclide scintigraphy to determine etiology (thyroid dysgenesis vs dyshormonogenesis) 3
• Family history: Inquire about family history of thyroid disorders 1
• Physical examination: Check for clinical signs of hypothyroidism (although most neonates appear normal) 4

Monitoring Protocol

1. Initial follow-up:

   • Measure serum free T4 at 2 weeks after starting treatment 3
   • Check TSH and free T4 at 1 month 3

2. Ongoing monitoring:

   • Monitor every 2 months until 6 months of age 3
   • Then every 3 months from 6 months to 3 years 3
   • Adjust dosage to maintain free T4 in the upper half of normal range and normalize TSH 5

3. Treatment goals:

   • Normalize thyroid function as rapidly as possible 4
   • Maintain free T4 in the upper half of the normal range 5
   • Keep TSH within normal range 5

Important Considerations

• Timing is critical: Treatment must begin within the first 2 weeks of life to prevent mental retardation 6
• False positives: Be aware that physiological TSH surge in the first 1-2 days after birth can cause false positive results 4
• Preterm infants: These babies may have delayed TSH elevation and require special consideration 7, 8
• Transient hypothyroidism: All infants with elevated TSH should be treated as having congenital hypothyroidism for the first 3 years of life 4
• Reevaluation: Consider reevaluation at age 3 years to assess need for lifelong therapy in cases where transient hypothyroidism is suspected 3

Pitfalls to Avoid

• Delaying treatment: Never delay treatment while waiting for imaging results 3
• Inadequate dosing: Insufficient levothyroxine dosing may lead to suboptimal neurodevelopmental outcomes 5
• Poor monitoring: Failure to monitor thyroid function regularly can lead to under or over-treatment 5
• Missing transient hypothyroidism: Even if transient, hypothyroidism requires treatment for at least 3 years 4

Early detection and prompt treatment of congenital hypothyroidism is one of the most successful preventive interventions in pediatric medicine, with >90% of affected children avoiding mental retardation when properly treated 6.