SummaryCongenital hypothyroidism represent one of the most common preventable causes of mental retardation The incidence of congenital hypothyroidism detected by screening varies from 1 in 3500 to 1 in 4500 Transient disorders of thyroid function detected at screening but disappear subsequently in a few days or weeks may be seen as transient primary hypothyroidism transient hyperthyrotropinaemia or transient hypothyroxinaemia Transient primary hypothyroidism: This disorders is characterized by low serum T4 and high TSH concentrations The prevalance varies geographically being higher in iodine deficient areas which is approximately 1 2000 1 8000 in Europe 1 50000 in USA Administration of iodine containing drugs to the mother in utero or in postnatal period amniotic injection of radiographic contrast agents for amniofetography or use of iodinated skin disinfectants in the neonate may induce hypothyroidism Premature and low birth weight infants are more susceptible to the externally applied iodine induced hypothyroidism Antithyroid drugs used in the pregnant woman with Graves disease may cause transient hypothyroidism by crossing the placenta TSH receptor blocking antibodies may also cause thyroid deficiency on the nervous system justify the treatment with thyroid hormones Therapy is subsequently discontinued according to the underlying cause If the diagnosis is not certain therapy may be continued up to 3 years of age and thyroid hormone status re evaluated after 6 weeks of therapy Transient hyperthyrotropinaemia: This is characterized by high TSH and normal T4 levels Intrauterine iodine excess or deficiency and intrauterine antithyroid drug exposure may result in transient hyperthyrotropinemia Affected infants do not require treatment but prolonged follow up is necessary to exclude the possibility of a permenant disorder such as an ectopic thyroid or an inborn detect in thyroid hormonogenesis Transient hypothyroxinaemia: Serum T4 is low TSH is normal Immaturity of hypothalamo pituitary thyroid axis is the main cause of this disorder which is seen in 3 9 of neonates with higher prevalence in the premature infants Serum T4 concentrations increase with progressive maturation The effect of transient hypothyroxinemia on mental developmental in early infancy is not known thus the treatment of affected infants is controversial In addition to these disorders low T3 syndrome in preterm infants is a normal condition which may last up to 6 7 weeks Key words: Transient Primary Hypothyroidism Congenital Hypothyroidism Neonatal Thyroid Disorders Hyperthyrotropinemia Hypothyroxinaemia Cretinism Goiter Topical Povidone Iodine

Congenital hypothyroidism represent one of the most common preventable causes of mental retardation The incidence of congenital hypothyroidism detected by screening varies from 1 in 3500 to 1 in 4500 Transient disorders of thyroid function detected at screening but disappear subsequently in a few days or weeks may be seen as transient primary hypothyroidism transient hyperthyrotropinaemia or transient hypothyroxinaemia Transient primary hypothyroidism: This disorders is characterized by low serum T4 and high TSH concentrations The prevalance varies geographically being higher in iodine deficient areas which is approximately 1 2000 1 8000 in Europe 1 50000 in USA Administration of iodine containing drugs to the mother in utero or in postnatal period amniotic injection of radiographic contrast agents for amniofetography or use of iodinated skin disinfectants in the neonate may induce hypothyroidism Premature and low birth weight infants are more susceptible to the externally applied iodine induced hypothyroidism Antithyroid drugs used in the pregnant woman with Graves disease may cause transient hypothyroidism by crossing the placenta TSH receptor blocking antibodies may also cause thyroid deficiency on the nervous system justify the treatment with thyroid hormones Therapy is subsequently discontinued according to the underlying cause If the diagnosis is not certain therapy may be continued up to 3 years of age and thyroid hormone status re evaluated after 6 weeks of therapy Transient hyperthyrotropinaemia: This is characterized by high TSH and normal T4 levels Intrauterine iodine excess or deficiency and intrauterine antithyroid drug exposure may result in transient hyperthyrotropinemia Affected infants do not require treatment but prolonged follow up is necessary to exclude the possibility of a permenant disorder such as an ectopic thyroid or an inborn detect in thyroid hormonogenesis Transient hypothyroxinaemia: Serum T4 is low TSH is normal Immaturity of hypothalamo pituitary thyroid axis is the main cause of this disorder which is seen in 3 9 of neonates with higher prevalence in the premature infants Serum T4 concentrations increase with progressive maturation The effect of transient hypothyroxinemia on mental developmental in early infancy is not known thus the treatment of affected infants is controversial In addition to these disorders low T3 syndrome in preterm infants is a normal condition which may last up to 6 7 weeks Key words: Transient Primary Hypothyroidism Congenital Hypothyroidism Neonatal Thyroid Disorders Hyperthyrotropinemia Hypothyroxinaemia Cretinism Goiter Topical Povidone Iodine