Earlier onset of treatment or increment in LT4 dose in screened congenital hypothyroidism: which as the more important factor for IQ at 7 years?
OBJECTIVE
To determine between timing and LT4 dose which was the more important factor for IQ at 7 years in screened congenital hypothyroidism (CH).


METHODS
131 children with CH born from 1979 to 1994 and 30 controls were studied. Mean age at recall: 22.8+/-1.1 days. Mean initial LT4:5.6+/-0.1 microg/kg/day.


RESULTS
Optimal global IQ (GIQ; 119+/-1.8) was obtained for a recall < or =15 days. Results for a recall after 3 weeks were lower (107.7 +/- 2.4). The IQ of infants treated before 21 days (117.1 +/-1.2) was identical to the IQ of those treated after this threshold was lower (108.6 +/- 1.7). No significant differences for GIQ were observed with various initial LT4. Infants treated with a dose of LT4 > or = 6 microg/kg/day had a higher performance IQ (117.3 +/-1.8 vs. 112.8+/- 1.2) compared with those treated with a dose < 6 microg/kg/day. The severity of CH and socio-economic levels were similar in all groups.


CONCLUSIONS
In this study, timing appears to be more important factor for the intellectual outcome.
Boileau
Pascal
P
General Outpatient Clinic, Hôpital St-Vincent-de-Paul, Paris, France.
Bain
Philippa
P
Rives
Solange
S
Toublanc
Jean-Edmond
JE
D002648:Child; D003409:Congenital Hypothyroidism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006132:Growth Plate / Q000473:pathology; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology*; D007231:Infant, Newborn; D007360:Intelligence / Q000187:drug effects*; D008297:Male; D015997:Neonatal Screening; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013974:Thyroxine / Q000008:administration & dosage* / Q000627:therapeutic use
D013974:Thyroxine