Congenital Hypothyroidism

Congenital hypothyroidism is thyroid hormone deficiency present from birth. Untreated severe disease causes irreversible neurodevelopmental impairment, making neonatal screening and early treatment critical.

Causes include thyroid dysgenesis, dyshormonogenesis and central hypothyroidism.

Most affected newborns initially appear normal.

Later findings include:

• Prolonged jaundice
• Poor feeding
• Constipation
• Hypotonia
• Excessive sleepiness
• Large fontanelle
• Macroglossia
• Umbilical hernia
• Hoarse cry
• Poor growth

Neonatal screening detects elevated TSH in primary hypothyroidism.

Confirm with serum:

• TSH
• Free T4

Do not delay treatment while waiting for imaging to determine the anatomical cause.

Start levothyroxine 10 to 15 micrograms/kg PO once daily as soon as diagnosis is confirmed or strongly suspected.

The goal is rapid normalization of free T4.

Monitor TSH and free T4 frequently during infancy because undertreatment risks neurodevelopmental injury while overtreatment also has adverse effects.

Early treatment within the first 2 weeks of life provides the best neurodevelopmental outcome.