School achievement is reduced in children
with congenital hyperthyroidism if it is severe and treatment is
inadequate
(March 2002)
The background of
the study. Early treatment of infants with congenital hypothyroidism
prevents the mental retardation that is so common in infants treated
later. However, some infants treated early have cognitive defects,
especially if their hypothyroidism is severe and treatment is suboptimal.
In this study infants with congenital hypothyroidism treated soon
after birth were evaluated during adolescence to determine the factors
that might affect their school achievement.
How the study was done. From 1979
to 1985 screening for congenital hypothyroidism was performed in
5,192,614 newborn infants in France. Among them, 1276 (0.024 percent)
had persistent hypothyroidism. Follow-up information about treatment
and school achievement (defined as entry into the sixth grade) was
obtained for 682 of these children in 1994 and 1998.
The results of the study. The mean
age of the 682 children (493 girls, 189 boys) at the start of treatment
was 23 days. The mean initial dose of thyroxine was 5.6 µg/kg/day.
The proportion of children with hypothyroidism who entered the
sixth grade at the usual time was similar to that of normal children.
Those who entered the sixth grade later were more likely to have
complete absence of thyroid tissue, lower serum thyroxine values
at diagnosis, a lower initial dose of thyroxine, and inadequate
treatment, as compared with those who did not enter the sixth grade
late. Factors not associated with late entry were age at the start
of treatment and the presence of symptoms and signs of hypothyroidism.
The conclusions of the study. Children
with severe congenital hypothyroidism and those who receive inadequate
treatment are at risk for poor school achievement.
The original article. Leger J, Larroque
B, Norton J, on behalf of AFDPHE. Influence of severity of congenital
hypothyroidism and adequacy of treatment on school achievement in
young adolescents: a population-based cohort study. Acta Paediatr
2001;90:1249-56.
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