Pediatria pre prax 3/2005

CONGENITAL HYPOTHYROIDISM

Congenital hypothyroidism (CH) appears in two forms. Endemic CH with various degrees of irreversible impairments of brain development in newborns is a consequence of mother and child iodine deficiency (ID) during pregnancy. The elimination of ID in the whole world belongs to priority programs of WHO and UNICEF, as an unnecessary cause of mental retardation of whole populations. In the Czech Republic (CR) iodine sufficiency has been attained since the year 2000 in 6 to 65-year-old population. However, not until 2003 in neonates. Sporadic permanent CH is connected with developmental and situational impairments of the thyroid gland (TG) or thyroid hormonal (TH) synthesis. The causes of primary CH are multifactorial. In the past 15 years mutations of genes which are acting during development and hormonogenesis of TG are being gradually revealed in 1–5 % of CH. Neonatal laboratory screening from mid – eighties of last century was essential for early diagnosis and treatment of primary CH. In positive cases from screening are 60 % of CH with anatomical and localization impairments and 30–35 % of patients with dyshormonogenesis have the TG in normal position, often with neonatal goiter. Treatment with levo-thyroxine, initial dose 10–15 mcg/day should be introduced not later than on the 14th day after birth. The prognosis in early treated CH is excellent, with normal life expentances. Screening of CH using TSH screening method is also a useful tool for monitoring of iodine supply in newborns at a population level. In CH screening results occur also transient impairments. A complete TG examination, in hypothyroidism substitutional treatment and a careful following up of these children is esssential. Longitudinal following of results on mass screening of CH in CR (> 1 000 000 screened newborns) revealed the stable incidence of primary permanent CH 1:4 230 live born neonates, twice more frequent in girls. In 193 of molecular genetic examined CH patients from the screening had gene mutation only in 1 % of cases. Other inborn impairments were more frequent in CH patients in comparison with remaining population and included cardiac impairments – 10× more frequently, m. Down-3× more frequently and hearing impairments 20× more frequently. During the period of total thyroxine screening method (1985–1996) the incidence of congenital defects of thyroxine-binding-globulin in the Czech neonates was established as 1:2 900 live born neonates.

Keywords: congenital hypothyroidism endemic form, sporadic form, newborn mass screening, etiology, treatment, prognosis.