Aetiology

Aetilogy of congenital hypothyroidism can be:

• permanent congenital hypothyroidism
  • primary hypothyroidism - the commonest causes include
    • thyroid agenesis
    • thyroid dysgenesis - due to a developmental anomaly of the thyroid gland e.g. - ectopic thyroid or hypoplastic thyroid as a result of a failure of normal descent of the thyroid in development
    • thyroid dyshormonogenesis – due to impaired hormone production
  • central or secondary hypothyroidism
    • most commonly presents as a part of a disorder causing congenital hypopituitarism
    • isolated TSH deficiency
    • thyrotropin-releasing hormone deficiency or resistance
• peripheral hypothyroidism
  • resistance to thyroid hormone
  • defect in thyroid hormone transport
• transient congenital hypothyroidism
  • maternal ingestion of antithyroid drugs
  • transfer of maternal TSH receptor blocking antibodies through the placenta
  • iodine deficiency – both in mother and neonate (1)

There is an association with Down's syndrome (1)

Reference:

• (1) Rastogi MV, LaFranchi SH. Congenital hypothyroidism. Orphanet J Rare Dis. 2010;5:17