Congenital Hypothyroidism

At birth, congenital hypothyroidism may be almost invisible. The infant can appear well while inadequate thyroid hormone is already placing brain development at risk, so newborn screening is a prevention strategy rather than a test reserved for symptomatic babies. An abnormal screen starts a rapid clinical pathway: obtain serum TSH and free T4, identify whether treatment must begin before confirmation is complete, and give levothyroxine promptly when congenital hypothyroidism is confirmed. Imaging may clarify whether the gland is absent, ectopic, or present but unable to synthesize hormone; it must not delay replacement. Safe tablet administration and reliable follow-up matter because the treatment benefit depends on sustained hormone exposure during the first years of life. For the REx-PN, the highest-priority decisions are recognizing the time-sensitive risk, interpreting the screening and confirmatory pattern, protecting levothyroxine absorption, and escalating severe biochemical or clinical findings.