A 3-week-old neonate has prolonged jaundice, hypotonia, coarse facies, large fontanelle, umbilical hernia, macroglossia, and constipation. TSH on newborn screening is 180 mIU/L (normal <10). What is the most common cause of congenital hypothyroidism?
- A Thyroid dysgenesis (aplasia, hypoplasia, or ectopia) ✓
- B Thyroid dyshormonogenesis (enzyme defect in thyroid hormone synthesis)
- C Maternal antithyroid antibody transfer
- D Central (secondary/tertiary) hypothyroidism
Explanation
Thyroid dysgenesis (abnormal thyroid gland development including aplasia, hypoplasia, and ectopia) accounts for approximately 75–80% of all cases of congenital hypothyroidism. Thyroid ectopia (lingual/sublingual thyroid) is the most common form of dysgenesis. Dyshormonogenesis accounts for ~15–20% and is usually autosomal recessive. Central hypothyroidism (TSH deficiency) accounts for ~1:25,000–100,000 births. Maternal antithyroid antibody-mediated neonatal hypothyroidism is transient. Early treatment with L-thyroxine before 2 weeks of age prevents intellectual disability (cretinism). Newborn TSH screening identifies the condition in the pre-symptomatic phase.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.