CONGENITAL HYPOTHYROIDISM

Key words: Congenital hypothyroidism, Neonatal screening (hypothyroidism)

The incidence of Primary Congenital Hypothyroidism (PCH) is about 1:2000. Most cases are due to a dysgenetic/ectopic thyroid. Only in a small minority of cases a defect in the iodine metabolism is present. Congenital hypothyroidism secondary to a defect of hypotalamic (TRH) or pituitary (TSH) function is very rare (1:50.000) and usually associated to other defects of pituitary hormones. Clinical signs may suggest the presence of hypothyroidism in the neonate, but only the neonatal screening (TSH and T4 serum level determination) guarantees a timely diagnosis for all cases. Investigations such as scintigraphy, sonography and X-ray of tibial nucleus are complementary aids for the diagnosis. Treatment (L-tyroxine, 8-10 mg/kg/die) must be started as soon as possible. A carefull follow up is needed. A transient neonatal hypothyroidism is possible, expecially in premature newborns. Other conditions may cause TNH but, as a rule, no treatment is needed in these cases.