Suppression of TSH in congenital hypothyroidism is significantly related to serum levels and dosage of thyroxine.
OBJECTIVE
To assess thyrotropin (thyroid-stimulating hormone; TSH) suppression and serum thyroxine (T(4)) concentrations in infants with congenital hypothyroidism in relation to T(4) dose and pretreatment parameters.


METHODS
A retrospective study of all cases treated in a single centre since neonatal screening began was performed.


RESULTS
In 54 infants treated with a mean daily T(4) dose of 9.8 microg/kg, the TSH concentration was suppressed (<6 mU/l) in 65% of the cases by 6 months with the serum T(4) level at the upper end of the infant reference range. Infants who suppressed their TSH later did not differ in pretreatment serum TSH or T(4) concentration. T(4) dose and serum T(4) level were lower in infants whose TSH was not suppressed.


CONCLUSIONS
TSH suppression in congenital hypothyroidism is significantly related to serum levels and dosage of T(4). We suggest that a delay in TSH suppression is mainly due to undertreatment.
Brown
J J
JJ
Children's Hospital, Leicester Royal Infirmary, Leicester, UK.
Datta
V
V
Sutton
A J
AJ
Swift
P G F
PG
D000375:Aging / Q000378:metabolism; D003409:Congenital Hypothyroidism; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000378:metabolism*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015997:Neonatal Screening; D012189:Retrospective Studies; D013972:Thyrotropin / Q000096:biosynthesis*; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use*
D013972:Thyrotropin; D013974:Thyroxine