In message <[log in to unmask]>, Dr J. Falconer
Smith <[log in to unmask]> writes
>For reasons that I do not yet fully understand
>(probably a simple clerical error)
>a patient with simple mild hypothyroidism
>(tsh 25miu/L, total T4 78 nmol/L free T4 9.1 nmol/L0
>had a thyroglobulin assay performed rather than a TBG
>(thyroid binding globulin
>)
>
>as is always the case is this sort of situation the
>thyroglobulin is not normal
>patient value 155 micrograms/L (quoted normal less than 60).
>
>The patient does not have a goitre and the neck is normal on
>examination (in this 30something female).
>
>I have found reference to patients with simple goitre having
>thyroglobulin levels up to 200 micrograms/L but nothing
>about simple goitre.
>
>The patient is now on thyroxine and I do intend to repeat
>the thyroglobulin as it should fall in this situation.
>
>It is difficult to prove a negative (ie that this patient does not
>have thyroid cancer) and the clinician is anxious and I am
>vexed by my inability to give him authorative advice (we don't
>do thyroglobulin assays - we send them away and the people we
>send them to don't know either).
>
>i bet there is someone out there who can advise!
>thanks (as ever) in advance
>
>James Falconer Smith
>Leicester
>
>ps the neck is normal on
>examination means on simple clinical examination (no imaging yet)
>
We occasionally get samples from patients who have a neck lump and the
doctor thinks that thyroglobulin can be used as a screening assay for
thyroid cancer. However thyroglobulin is detectable in normals (hence
the meaningless normal range) so is not useful as a tumour marker until
thyroid tissue has been cleared by definitive surgical clearance and the
presence of thyroglobulin in the serum indicates the presence of
extrathroidal tissue (presumably metastatic - but depends how good your
surgeon was !). The level of thyroglobulin in non malignant conditions
depends on the thyroid and is increased in thyroid inflammatory disease,
autoimmune thyroiditis being common, high levels beyond the "normal
range" may simply indicate thyroiditis. What is the thyroid antibody
status of the patient ? I have little experience as to the levels seen
in such cases but the level you indicate does appear possible with
thyroid inflammation.
There are a number of other factors which will also affect the
interpretation of the result, such as the type of assay used, some being
more influenced by antibodies than others, and whether any attempt was
made to measure recovery in the assay to indicate interference.
Trevor
Dr. T.A. Gray
Department of Clinical Chemistry
Northern General Hospital
Sheffield S5 7AU
0114 271 4309
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