Significance of Early Diagnostic Data in Congenital Hypothyroidism: Report of the Subcommittee on Neonatal Hypothyroidism of the European Thyroid Association
The objective of this work has been to evaluate the natural history of thyroid dysgenesis during early life in order to explain why infants with congenital hypothyroidism and with similarly low serum T4 at diagnosis frequently have markedly different clinical signs of hypothyroidism. Standardized data were collected in an international collaborative study from 181 infants (132 females and 49 males) with congenital hypothyroidism detected by neonatal screening and in whom thyroid scanning performed before therapy allowed a precise etiological diagnosis i.e. thyroid agenesis, ectopic thyroid or dyshormonogenesis. In thyroid agenesis, serum thyroxine (T4) at screening was low but not necessarily undetectable and rapidly decreased thereafter. In ectopic thyroids, serum T4 decreased by 40% between screening and diagnosis in approximately one third of the infants. Serum thyroglobulin (Tg) was not necessarily undetectable in thyroid agenesis nor detectable in ectopic thyroids. There was only a poor relationship between serum T4 and bone maturation at diagnosis in congenital hypothyroidism. The data suggest that loss of functional capacity of the dysgenesic thyroid tissue occurs during early life in some infants with congenital hypothyroidism and that serum Tg cannot replace thyroid scintigraphy in the evaluation of infants with congenital hypothyroidism.
KeywordsThyroid Tissue Congenital Hypothyroidism Neonatal Screening Serum Thyroglobulin Ectopic Thyroid
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