Congenital hypothyroidism: influence of disease severity and L-thyroxine treatment on intellectual, motor, and school-associated outcomes in young adults.
OBJECTIVE
To describe intellectual, motor, and school-associated outcome in young adults with early treated congenital hypothyroidism (CH) and to study the association between long-term outcome and CH variables acting at different points in time during early development (CH severity and early L-thyroxine treatment levels [0-6 years]).


METHODS
Neuropsychological tests were administered to all 49 subjects with CH identified during the first 3 years of the Norwegian neonatal screening program (1979-1981) at a mean age of 20 years and to 41 sibling control subjects (mean age: 21 years).


RESULTS
The CH group attained significantly lower scores than control subjects on intellectual, motor, and school-associated tests (total IQ: 102.4 [standard deviation: 13] vs 111.4 [standard deviation: 13]). Twelve (24%) of the 49 CH subjects had not completed senior high school, in contrast to 6% of the control subjects. CH severity (pretreatment serum thyroxine [T4]) correlated primarily with motor tests, whereas early L-thyroxine treatment levels were related to verbal IQ and school-associated tests. In multiple regression analysis, initial L-thyroxine dose (beta = 0.32) and mean serum T4 level during the second year (beta = 0.48) predicted Verbal IQ, whereas mean serum T4 level during the second year (beta = 0.44) predicted Arithmetic.


CONCLUSIONS
Long-term outcome revealed enduring cognitive and motor deficits in young adults with CH relative to control subjects. Verbal functions and Arithmetic were associated with L-thyroxine treatment variables, suggesting that more optimal treatment might be possible. Motor outcome was associated with CH severity, indicating a prenatal effect.
Oerbeck
Beate
B
Regional Center for Child and Adolescent Psychiatry, Region East and South, Oslo, Norway. beate.orbeck@r-bup.no
Sundet
Kjetil
K
Kase
Bengt F
BF
Heyerdahl
Sonja
S
D000328:Adult; D003072:Cognition Disorders / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D003409:Congenital Hypothyroidism; D004521:Educational Measurement; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications / Q000188:drug therapy / Q000453:epidemiology; D007231:Infant, Newborn; D007361:Intelligence Tests; D007859:Learning Disabilities / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D008297:Male; D015997:Neonatal Screening; D009483:Neuropsychological Tests; D009664:Norway / Q000453:epidemiology; D011596:Psychomotor Disorders / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D035781:Siblings; D012959:Socioeconomic Factors; D013974:Thyroxine / Q000008:administration & dosage / Q000627:therapeutic use*; D016896:Treatment Outcome
D013974:Thyroxine