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Congenital hypothyroidism is the most frequent inborn endocrine disorder and the most frequent disease diagnosed by nation-wide newborn screeening. 80-85% of permanent cases is caused by a defective thyroid development - thyroid dysgenesis. Remaining cases are caused by defects of thyroid hormone biosynthesis - dyshormonogenesis. Early and adequate substitution treatment together with a good family compliance are the main factors playing role in psychomotor, mental and somatic development of the majority of children with congenital hypothyroidism. [ABSTRACT FROM AUTHOR]

This survey article connects physiology of anatomical and functional development of thyroid gland (including genetic influence during thyroid morphogenesis and hormonogenesis) with newborn care. Disorders of thyroid development and function may lead to congenital hypothyroidism, which, unless treated in due time, causes irreversible impairment of child's development, especially in the area of neurocognitive functions. A functioning newborn screening programme can prevent mental and other impairments by early diagnosing hormone levels and enabling a timely start of an appropriate term newborn treatment with L-thyroxine. Mild forms of thyroid dysgenesis and dyshormonogenesis which can be functionally asymptomatic at birth may not show during newborn screening. Later on, they develop into non-immune based hypothyroidism or they can occur in families with congenital hypothyroidism. In case of newborn hyperthyrotropinemia, management strategy should be based on TSH levels during week 2 after delivery. Therapy guidelines for transient hypothyroxinemia of prematurity are still being discussed. Triiodothyronine substitution is recommended in newborns with a prolonged course of a severe disease and if the sick euthyroid syndrome is proved. If the therapy is not indicated, children should be included in a long-term follow-up programme. [ABSTRACT FROM AUTHOR]

This survey article connects physiology of anatomical and functional development of thyroid gland with maternal iodine supplementation and maternal disorders of thyroid gland. The fetus is fully dependent on maternal thyroid hormones until week 14 to 16 of gestation. The production of its own thyroid hormones gradually increases in the third trimester. Maternal iodine supplementation is essential for the developing fetus in the whole course of gestation. If the mother suffers from thyroid disease or iodine deficiency, the child's neurocognitive functions are more affected despite being treated for congenital hypothyroidism in time. [ABSTRACT FROM AUTHOR]

Pendred syndrome (PS, OMIM #274600) is an autosomal recessive genetic disease, which becomes manifest in a combination of sensoric-neural deafness and dyshormonogenetic goitre. In the PS we frequently encounter abnormal formation of inner ear structures - enlarged vestibular aqueduct (EVA) and/or Mondini dysplasia (MD). PS is caused by mutations in the SLC26A4 gene (called also PDS gene, OMIM *605646), which encodes the anion transporter pendrin, expressed especially in thyroid gland and the inner ear. Pendrin in the thyroid gland is localized on the apical pole of thyreocytes. Its main function is the transport of iodine into colloids in follicle lumen, where it is subsequently bound to organic molecules. The affection of thyroid gland in the Pendred syndrome becomes manifest mostly in the second decade of life under the picture of euthyroid and hypothyroid goitre, rarely there is dyshormogenesis at birth and the disease is then diagnosed in the newborn screening for congenital hypothyreosis. The mutation in the SLC26A4 gene causes also a non-syndrome hearing loss associated with EVA (formerly called DFNB4, OMIM #600791). Only recently the digenetic heredity has been established -- mutation in the SLC26A4 gene in combination with a mutation in the FOXI1 gene (OMIM *601093) or KCNJ10 gene (OMIM *602208). PS represents the most frequent syndrome deafness and the SLC26A4 gene is apparently the second most frequent gene responsible for AR non-syndrome hearing loss (after GJB2 gene for Connexin 26, which is responsible for 40% of AR non-syndrome hearing loss).A recently undertake study in the Czech Republic confirmed mutation in the SLC26A4 gene in 8.5% of predominantly child patients with inborn hearing loss; however only less than 27% of these children displayed a completely expressed PS (after puberty in all of them). Thanks to molecular genetic examination it is therefore possible to predict with high probability the development of thyroid gland disorder and to prevent the development of goitre by an early intervention. The examination of the SLC26A4 gene in presently available in the Czech Republic. [ABSTRACT FROM AUTHOR]