Thyroid Research Thyroid Research Archive Congenital

Thyroid radioiodine imaging is superior to ultrasonography in determining the cause of congenital hypothyroidism

(March 2004)

The background of the study. Congenital hypothyroidism is usually caused by developmental abnormalities of the thyroid gland; the gland may be absent or there may be only a small amount of thyroid tissue, which is often abnormally located. The remaining infants have a normal-sized or enlarged thyroid gland but cannot synthesize thyroid hormone. This study was done to compare the efficacy of thyroid radioiodine scans and thyroid ultrasonography in distinguishing among the causes of congenital hypothyroidism.

How the study was done. The study subjects were 66 infants with congenital hypothyroidism identified by newborn screening and confirmed days after birth at a single hospital in France. Thyroid imaging 30 minutes after intravenous injection of iodine-123 and thyroid ultrasonography were done at that time.

The results of the study. Based on iodine-123 imaging, 42 (64 percent) of the infants had ectopic thyroid tissue, 12 (18 percent) had no thyroid tissue, and 12 (18 percent) had normally located thyroid tissue. Among the 42 infants in the ectopic thyroid group, ultrasonography revealed ectopic thyroid tissue in 9 and no thyroid tissue in the other 33. Among the 12 infants with no thyroid tissue, as determined by iodine-123 scan, ultrasonography revealed a normally located large thyroid gland in one and a normally located small thyroid gland in one. In five infants, ultrasonography was more informative than iodine-123 scanning in defining the thyroid gland.

The conclusions of the study. Scanning with iodine-123 is more informative than thyroid ultrasonography in determining the cause of congenital hypothyroidism.

The original article. Bubuteishvili L, Garel C, Czernichow P, Leger J. Thyroid abnormalities by ultrasonography in neonates with congenital hypothyroidism. J Pediatr 2003;143:759-64.