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Intellectual development in children with congenital hypothyroidism in relation to recommended thyroxine treatment
S Heyerdahl1, B F Kase, S O Lie
1Department of Pediatric Research, National Hospital, Oslo, Norway.
Insights
Optimizing serum thyroxine levels in infants with congenital hypothyroidism is crucial for intellectual development. Early treatment and maintaining adequate thyroxine levels during the first two years promote better cognitive outcomes at ages 2 and 6.
Area of Science:
- Pediatrics
- Endocrinology
- Neuroscience
Background:
- Congenital hypothyroidism (CH) requires timely treatment to prevent cognitive deficits.
- Neonatal screening enables early identification and intervention for CH.
- The impact of serum thyroxine levels on neurodevelopment in CH requires further elucidation.
Purpose of the Study:
- To investigate the correlation between serum thyroxine levels and intellectual development in children with CH.
- To identify optimal thyroxine levels for cognitive outcomes in early childhood.
Main Methods:
- Longitudinal study of 46 Norwegian children with CH identified via neonatal screening.
- Assessment of serum thyroxine levels during the first two years of life.
- Evaluation of intellectual development using the Bayley Scales of Infant Development and Wechsler Preschool and Primary Scale of Intelligence at 2 and 6 years.
Main Results:
- Serum thyroxine levels in the first two years positively correlated with Mental Development Index (MDI) at 2 years and Verbal IQ at 6 years.
- Children with mean serum thyroxine >180 nmol/L in the first year showed significantly higher MDI and Verbal IQ.
- Boys exhibited lower MDI at 2 years and higher thyroid-stimulating hormone levels compared to girls.
Conclusions:
- Serum thyroxine levels are critical for intellectual development in children with CH.
- Maintaining thyroxine levels within the upper reference range during the first two years is associated with optimal cognitive development.
- No toxic effects of high thyroxine levels were observed; however, elevated levels in girls aged 2-4 years were linked to lower Performance IQ at age 6.
Abstract:
The relationship between the treatment serum thyroxine level and intellectual development at 2 and 6 years was investigated in 46 Norwegian children with congenital hypothyroidism identified by neonatal screening. The level of serum thyroxine during the first 2 years was positively correlated with the Mental Development Index at 2 years of age (Bayley Scales of Infant Development) and the Verbal IQ at 6 years of age (Wechsler Preschool and Primary Scale of Intelligence). Children with a mean serum thyroxine level greater than 180 nmol/L (14 micrograms/dl) during the first year had a significantly higher Mental Development Index at 2 years and Verbal IQ at 6 years than children with serum thyroxine values less than 129 nmol/L (10 micrograms/dl). Boys had a lower Mental Development Index at 2 years of age than girls (86.9 vs 105.1; p less than 0.001) and a higher frequency of elevated serum levels of thyroid-stimulating hormone during the first year (p = 0.001). No signs of toxic effects of a high hormone level at the time of IQ assessment were detected. However, high serum levels of thyroxine at ages 2 to 4 years in girls were related to lower Performance IQ at age 6 years. The results demonstrate that the serum level of thyroxine is of importance in relation to intellectual development. Thyroxine levels above the upper reference range during the first 2 years were related to best intellectual development at 2 and 6 years.