We seem to be seeing an appreciable number of children (not neonates) in
whom the TSH is higher than our quoted adult reference range of 0.27-4.2
(taken from the Roche Elecsy TSH kit insert). Clearly this may only be our
perception since normal TSH values are not scrutinised. FT4 is normal
although sometimes towards the lower end of the ref range whilst FT3 is
usually raised above the adult RR.
Searching the somewhat limited literature confirms that FT3 is higher in
chidren but for TSH the situation appears much less certain. Most papers
suggest that after the neonatal period TSH falls to adult values. One more
recent paper - Zurakowski Clin Chem 1999; 45:1087, using a DELFIA assay
showed quite a marked fall in the upper reference interval (6.3 age 1-11
monhs to 3.9 age 16-20). Are we seeing 'subclinical hypothyroidism' or just
applying an inappropriate reference range (and before anyone asks our EQA
performance is ok!)?
Anne Tarn
Anne Tarn
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