Thyroid Research Thyroid Research Archive Congenital

Severe hypothyroidism and slow onset of adequate treatment are associated with learning and memory deficits in children with congenital hypothyroidism

(March 2002)

The background of the study. Early treatment of children with congenital hypothyroidism prevents the developmental delay associated with later treatment, but some children treated early have cognitive impairment, including limitations in attention, language, and memory. This study evaluated the relationships between specific cognitive abilities and the severity and adequacy of treatment of children with congenital hypothyroidism.

How the study was done. The study subjects were 62 children 7 to 12 years old who had congenital hypothyroidism detected by neonatal screening between 1986 and 1992. Among them, 18 had no thyroid tissue (athyreosis), 27 had abnormally located thyroid tissue, and 17 had normally located thyroid tissue. On average, thyroxine (T4) treatment was initiated 17 days after birth; the initial dose was 9 µg/kg/day.

The tests done for the study included the Vocabulary, Arithmetic, Coding, and Symbol Search subtests of the Wechsler Intelligence Scale for Children, and the Children's Memory Scale.

The results of the study. The clinical characteristics, serum thyrotropin (TSH) concentrations, and initial doses of thyroxine were similar in the children with the three different types of thyroid disease.

The children in the athyreosis group were less likely to have normal serum TSH concentrations during the first three months of treatment, and their dose of T4 was adjusted more often during the first year of treatment, as compared with the other two groups. These children scored lower on many components of the Wechsler Intelligence Scale for Children, whereas the scores for the other two groups were similar. The scores on these tests and the Children's Memory Scale were lower in all children who had high serum TSH concentrations during the first three months of treatment, as compared with the children with normal concentrations at these times.

The conclusions of the study. Among children with congenital hypothyroidism, those with athyreosis and those in whom treatment does not lower TSH secretion quickly are at increased risk for learning and memory deficits later in life.

The original article. Song S-I, Daneman D, Rovet J. The influence of etiology and treatment factors on intellectual outcome in congenital hypothyroidism. J Dev Behav Pediatr 2001;22:376-84.

Thyroid Research Archive
Congenital Hypothyroidism

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