Intellectual development in children with congenital hypothyroidism in relation to recommended thyroxine treatment.
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.
Heyerdahl
S
S
Department of Pediatric Research, National Hospital, Oslo, Norway.
Kase
B F
BF
Lie
S O
SO
D000704:Analysis of Variance; D002648:Child; D002657:Child Development / Q000187:drug effects* / Q000502:physiology; D002675:Child, Preschool; D015331:Cohort Studies; D003409:Congenital Hypothyroidism; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy; D007360:Intelligence / Q000187:drug effects* / Q000502:physiology; D007361:Intelligence Tests; D008297:Male; D012727:Sex Characteristics; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood* / Q000494:pharmacology / Q000627:therapeutic use
D013972:Thyrotropin; D013974:Thyroxine