LONG-TERM NEURODEVELOPMENTAL CORRELATES OF TREATMENT ADEQUACY IN SCREENED HYPOTHYROID CHILDREN

Abstract

To assess the later effects of treatment adequacy in children with congenital hypothyroidism (CH) diagnosed by newborn screening, we correlated performance on neurobehavioural and psychoeducational tests with T4 levels and dosage L-thyroxine at diagnosis and specific intervals throughout childhood. Of our original cohort of 108 screened CH children followed since birth, 95 were available for testing at 7 years and 70 at 9 years and the third grade; controls consisted of siblings and classmates (school data only). Tests included standardized age-appropriate measures of cognitive abilities, behaviour, school achievement, and class performance based on teacher report. Compared with controls, CH did more poorly on tests of visuospatial ability, arithmetic, reading comprehension, auditory memory, class learning, and attention. Correlations revealed that (i) initial disease severity was associated with subsequently poorer verbal, visuoperceptual, and graphomotor abilities; (ii) higher starting dosage of L-thyroxine with better spatial, numerical, and auditory processing skills; (iii) higher dose in infancy and early childhood with greater hyperactivity and less adequate memory and attention but not with poorer cognitive abilities; (iv) high concurrent T4 values with poorer memory and attention, arithmetic, graphomotor skills, and class behaviour. These results suggest that while a higher dose may be necessary during the newborn period when the brain is undergoing rapid development, subsequent levels should be monitored closely to minimize behaviour problems and less adequate attention, memory, and arithmetic achievement associated with high serum T4 values.