Congenital hypothyroidism: long-term outcome.

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.