Long-term effects of L-thyroxine therapy for congenital hypothyroidism.
OBJECTIVE
To study the effects of initial and concurrent dose levels of L-thyroxine on ability and behavior in children with congenital hypothyroidism.


METHODS
An existing database, involving a large cohort of children with congenital hypothyroidism detected by neonatal screening, was analyzed retrospectively. There were 94 children: 89 were assessed at age 7 years for intelligence and selective cognitive abilities, and 87 at age 8 years for behavior, achievement, and selective abilities.


RESULTS
Subjects were stratified by median split into low and high starting dose groups. The high-dose group performed better on indexes of intelligence, verbal ability, and memory but had more behavior problems reflecting increased anxiety, social withdrawal, and poorer concentration. The dose of L-thyroxine at age 8 years was negatively correlated with memory task performance.


CONCLUSIONS
A higher starting dose of L-thyroxine is beneficial for subsequent intellectual outcome in children with congenital hypothyroidism but may be associated with internalizing behavior problems.
Rovet
J F
JF
Department of Pediatrics (Endocrinology Division), University of Toronto, Canada.
Ehrlich
R M
RM
D002648:Child; D002653:Child Behavior Disorders / Q000209:etiology*; D003409:Congenital Hypothyroidism; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000523:psychology; D007223:Infant; D007231:Infant, Newborn; D007360:Intelligence / Q000187:drug effects*; D008297:Male; D011446:Prospective Studies; D011581:Psychological Tests; D013974:Thyroxine / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use
D013974:Thyroxine