Clinical Relevance of Molecular Diagnosis in Patients with Congenital Hypothyroidism

Congenital hypothyroidism, defined as the functional deficiency of thyroid hormones present at birth, is the most frequent endocrine disorder in pediatric patients with an incidence estimated in 1:2,0004,000 newborns. Significantly, iodide deficiency still remains as the leading cause of hypothyroidism at birth [1]. However, in iodidesufficient countries, a number of recent studies indicates that 58% to 69% of congenital hypothyroidism is caused by genetic abnormalities resulting in thyroid dysgenesis, including thyroid (hemi)-agenesis, hypoplasia and ectopy. Meanwhile 31% to 42% of the patients have eutopic thyroid gland consistent with genetic defects that impair thyroid hormone synthesis, also called dyshormonogenesis [2]. Other less common genetic causes of congenital hypothyroidism include central hypothyroidism or defects in peripheral thyroid hormone action, cellmembrane transport, or metabolism [3-5].