Which of the following is NOT an early sign of congenital hypothyroidism in the neonate?

• A. Growth retardation
• B. Hyperthermia
• C. Large anterior and posterior fontanelle
• D. Lethargy

Answer: (B)

Neonatal congenital hypothyroidism reveals a slowdown of metabolic processes. Because thyroid hormone drives thermogenesis and energy use, insufficient hormone leads to a cooler, lethargic infant with reduced responsiveness and feeding, rather than fever. That hypometabolic state is why hyperthermia is not an early sign.

Early clues you’d expect include lethargy and poor feeding from the outset, along with hypotonia. Prolonged neonatal jaundice is common because bilirubin conjugation is slowed. The fontanelles may be relatively large due to delayed bone maturation, reflecting slowed development. Growth retardation tends to appear as the infant’s growth falters over weeks to months rather than as an immediate early sign. Understanding these features helps distinguish congenital hypothyroidism from conditions that cause fever or hypermetabolism.