Neonatal screening for congenital hypothyroidism in Estonia

Screening for congenital hypothyroidism was carried out by measuring thyroid stimulating hormone (TSH) on dried blood spots (mean + 2SD cut off value 12 microU/ml) by fluoroimmunoassay using DELFIA kits. A total of 20,021 infants were screened, and seven cases with congenital hypothyroidism were detected, giving an incidence of congenital hypothyroidism of 1:2860 (female:male ratio 6:1). In four of seven infants with congenital hypothyroidism (57%) the mother also had thyroid disease, supporting the importance of genetic factors as a cause of congenital hypothyroidism. Transient hyperthyrotropinaemia occurred in 654 infants (recall rate 3.3%). There was a significant association of transient hyperthyrotropinaemia only with cardiac failure at birth or caesarean section (p < 0.01). Family studies showed no predisposition to thyroid diseases associated with a transient increase of TSH.