Congenital hypothyroidism. The effect of stopping treatment at 3 years of age
T. Davy, D. Daneman, P. G. Walfish and R. M. Ehrlich
Fifty-six children with congenital hypothyroidism diagnosed by neonatal
screening were reviewed at 3 years of age or older. The presence or absence
of the thyroid gland was determined by radionuclide scanning prior to
treatment in the newborn period. Thyroxine therapy was discontinued in
those children who did not have anatomic defects or a secondary rise in
their thyrotropin (thyroid-stimulating hormone [TSH]) level once it was
suppressed by thyroid hormones. Sixteen of 17 children developed a low
thyroxine and an elevated TSH level within three to six weeks. One child
was not receiving thyroxine for nine months and was clinically and
biochemically euthyroid. We conclude that (1) newborn thyroid scans are
useful to determine the cause of hypothyroidism, (2) a secondary rise in
the TSH level indicates permanent hypothyroidism, (3) only about one third
of infants whose condition is diagnosed by newborn screening will qualify
for a trial off therapy at 3 years of age, (4) only 1% to 2% of infants
whose condition is diagnosed by newborn screening have transient
hypothyroidism, and (5) a three-week period of hormone withdrawal after the
age of 3 years seems adequate and safe to confirm permanent hypothyroidism.
