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Congenital hypothyroidism: long-term outcome
1The Hospital for Sick Children and University of Toronto, Ontario, Canada. joanne.rovet@sickkids.on.ca
Insights
Children with congenital hypothyroidism (CH) treated early may still experience subtle neurocognitive deficits, particularly in visuospatial, memory, and attention skills, persisting into adolescence.
Area of Science:
- Pediatric Endocrinology
- Neurodevelopmental Pediatrics
- Thyroid Research
Background:
- Congenital hypothyroidism (CH) necessitates newborn screening and early treatment to prevent intellectual disability.
- Despite early intervention, a transient period of thyroid hormone deficiency can occur, impacting brain development.
- Thyroid hormone is crucial for various stages of brain maturation, with different regions having distinct requirements.
Purpose of the Study:
- To investigate the long-term neurocognitive outcomes in adolescents with CH identified through newborn screening.
- To determine if subtle neurocognitive deficits persist into adolescence despite early and adequate treatment.
- To correlate these deficits with the severity of early hypothyroidism and thyroid hormone levels.
Main Methods:
- Longitudinal follow-up of a large cohort of Toronto-based children with CH since 1980.
- Comparison of neurocognitive assessments in 48 adolescent subjects with CH against matched controls.
- Analysis of correlations between neurocognitive deficits and disease/treatment factors, including thyroxine (T4) levels.
Main Results:
- Adolescents with CH showed persistent deficits in visuospatial abilities, memory, and attention compared to controls.
- These deficits were correlated with the severity of early hypothyroidism.
- Negative relationships between attention indices and current thyroxine (T4) levels suggest a role in attention regulation.
Conclusions:
- Early treatment of CH prevents severe intellectual disability but subtle neurocognitive deficits can persist into adolescence.
- The severity of early thyroid hormone deficiency is a key factor influencing long-term neurocognitive outcomes.
- Thyroid hormone plays a role in the regulation of attention, even in treated individuals.
Abstract:
Although mental retardation associated with congenital hypothyroidism (CH) is prevented by newborn screening and early treatment, affected children still undergo a brief period of thyroid hormone deficiency reflecting etiology of thyroid disease, illness severity, and treatment factors. Because thyroid hormone is essential for normal brain development and because some processes require thyroid hormone in the period when thyroid hormone was lacking, children with CH treated early may still have subtle neurocognitive deficits. As the period when thyroid hormone is needed differs for different brain regions, there may be different types of deficits depending on when thyroid hormone levels were insufficient. Since 1980, we have been following a large cohort of Toronto-based children with congenital hypothyroidism identified by newborn screening from infancy to adolescence. Early findings revealed a 5-10-point decline in IQ, poorer visuomotor and visuospatial abilities, delayed speech and language development, selective neuromotor deficiencies, and poorer attention and memory skills, which were correlated with different disease and treatment factors. Now a comparison between 48 subjects at adolescence and matched controls indicates that deficits persist in visuospatial, memory, and attention domains and these are correlated with severity of early hypothyroidism. Negative relationships between attention indices and thyroxine (T4) elevations at time of testing also suggest a role for thyroid hormone in the regulation of attention.