Does anyone have any data or references to the half life of T4, when
given to treat hypothyroidism?
If this is hours rather than days, could the length of time from the
patient taking the last dose to blood sampling significantly alter the
serum thyroid hormone results?
In these patients we do sometimes see a relatively high FT4 compared to
the TSH, e.g. a raised TSH with FT4 at the upper limit of normal or
there abouts. Our assays have been in control at the time. I know there
are other possible explanations, but am I right that this could be due
to poor patient compliance (raising the TSH), with the conscience
stricken patient taking too many T4 tablets to compensate (pushing up
the FT4) just before a clinic appointment?
Has anyone carried out or come across a study looking at this?
I hope to gain from your many years of collective experience of thyroid
function.
Best wishes
Steve
Dr S J Frost
Clinical Biochemistry Department
The Princess Royal Hospital
Haywards Heath
West Sussex
England
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