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.
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