In congenital hypothyroidism, when should thyroid hormone replacement therapy be started?

• A. Only if symptomatic
• B. Not usually required in newborns
• C. After confirm
• D. Promptly for all hypothyroid infants

Answer: (D)

Thyroid hormone is essential for brain development in the newborn period, so any deficiency can lead to permanent neurocognitive impairment if treatment is delayed. In congenital hypothyroidism, initiating thyroid hormone replacement promptly prevents these irreversible deficits, making early therapy crucial for every affected infant, even if they appear well or asymptomatic at birth. Because newborn screening can identify CH before symptoms arise, treatment should begin immediately when CH is suspected or confirmed, rather than waiting for symptoms or for full confirmatory testing. Delaying therapy until after confirmation or until symptoms appear risks missed developmental windows and worse outcomes. In practice, start levothyroxine promptly and adjust the dose based on serial thyroid function tests and clinical response.