Congenital hypothyroidism in infants is most commonly associated with which finding?

• A. Excessive sleepiness
• B. Diarrhea
• C. Tachycardia
• D. Failure to thrive

Answer: (C)

Infants with congenital hypothyroidism have slowed metabolism and impaired growth, so signs reflect poor energy and development. Among the options, failure to thrive best fits this pattern because reduced thyroid hormone limits growth and weight gain, making growth lag a prominent and recognizable feature in infancy. Tachycardia would be unexpected here—hypothyroidism tends to cause a slower heart rate (bradycardia) rather than a rapid one. Diarrhea is not typical (constipation is more common), and while excessive sleepiness can occur, it’s the growth impairment that most clearly signals hypothyroidism in this context.