Benefits and Risks of Thyroid Scintigraphy in Congenital Primary Hypothyroidism

Abstract

The diagnosis on the basis of low serum thyroxine level with high thyrotropin level of congenital primary hypothyroidism in newborn screening programs fails to distinguish between transient hypothyroidism and ectopic thyroid, athyrosis, dyshormonogenesis, or transient hyperthyrotropinemia. The correct use of neonatal thyroid scintigraphy aids in making a specific anatomic diagnosis. We scanned 18 of 24 infants who had congenital hypothyroidism detected from screening 116,300 newborn infants, using Tc-99m in the first 8, then I-123 in 10. Eight infants were found to be athyrotic and 2 had ectopic glands; in 8, the thyroid gland appeared normal. Probably due to initially poor technique, 1 “athyrotic” infant was later found to be normal. We suggest that before initiating long-term thyroid medication, the specific anatomic and functional diagnosis be confirmed by this low-dose thyroid scintigraphic technique which has been optimized for newborn infants.