Thyroid Research Thyroid Research Archive Congenital

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.

Thyroid Research Archive
Congenital Hypothyroidism

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