Original ArticleNeurodevelopmental Outcomes in Congenital Hypothyroidism: Comparison of Initial T4 Dose and Time to Reach Target T4 and TSH
Section snippets
Methods
In our original study, 47 subjects were randomized into 1 of 3 initial L-thyroxine dosage groups: 37.5 μg, 50 μg, and 62.5 μg for 3 days followed by 37.5 μg daily (equivalent to 10.9, 14.5, and 17.7 μg/kg/day for 3 days followed by 10.6 μg/kg/day, respectively). Serum free T4, T4, free triiodothyronine (T3), T3, and TSH levels were measured before treatment and at 3 and 7 days and 2, 4, 8, and 12 weeks after initiation of L-thyroxine therapy. In accordance with the study protocol, no dosage
Comparison of the Original 3 Treatment Cohorts
Average FSIQ was 100.6 in the 50-μg loading dose group and 95.3 in the 62.5-μg group. The lower-dose group (37.5 μg) as a whole scored significantly lower than the other groups, with an average FSIQ of 89.5 (P < .05). In this group, the mean Mullen score of the 4 youngest subjects was 80.75, and the FSIQ scores of the others averaged 95.3; thus the younger subjects scored significantly lower than the older subjects. The 3 treatment cohorts did not differ in terms of VIQ and PIQ scores. There
Discussion
Overall, IQ scores were similar in the original 3 treatment cohorts. The 37.5-μg group did score lower in FSIQ, possibly reflecting the larger proportion of younger subjects in this group who took the Mullen test (because cognitive scores tend to be less reliable in very young children). The Mullen test emphasizes speech and language development, whereas Wechsler tests measure verbal abilities, so this pattern may reflect the delayed language acquisition with later catch-up in the younger
References (16)
In search of the optimal therapy for congenital hypothyroidism
J Pediatr
(2004)The importance of early management in optimizing IQ in infants with congenital hypothyroidism
J Pediatr
(2000)- et al.
Influence of timing and dose of thyroid hormone replacement on development in infants with congenital hypothyroidism
J Pediatr
(2000) - et al.
Initial treatment dose of L-thyroxine in congenital hypothyroidism
J Pediatr
(2002) Effects of neonatal screening for hypothyroidism: prevention of mental retardation by treatment before clinical manifestations
Lancet
(1981)- et al.
Congenital hypothyroidism: influence of disease severity and L-thyroxine treatment on intellectual, motor, and school-associated outcomes in young adults
Pediatrics
(2003) Long-term neuropsychological sequelae of early-treated congenital hypothyroidism: effects in adolescence
Acta Paediatr Suppl
(1999)Congenital hypothyroidism: etiologies, diagnosis, and management
Thyroid
(1999)
Cited by (0)
Supported in part by U.S. Public Health Service grant 5-M01-RR000334.