TSH Antibody level and Plasma TSH level - what is the difference?

[Katkin1]

I have had both tested and the readings are different. Does anyone know what the difference is between the two tests please?

[PinkNinja]

TSH is the hormone that is released by the pituitary gland to tell the thyroid gland to produce thyroid hormones. TSH antibodies bind the the TSH receptors in the thyroid, thus stimulating them to produce thyroid hormones, or so I understand it. It is a test for Graves disease.

These are two different tests. Plasma TSH level tests how much TSH is in the blood and TSH antibody level is how many TSH receptor antibodies there are.

I think that is right but I'm sure someone will correct me if I've got it wrong. But they are definitely two different tests for two different things

Carolyn x

[helvella Administrator Thyroid UK in reply to PinkNinja]

Trouble is, to be pedantic, there can be TSH antibodies (TSHab) and TSH receptor antibodies (TRab)!

Oh - and the naming conventions are to pot - TRab are called different things in different documents.

TRab are of two types - they either block the TSH receptor or they stimulate it. If you are tested for TRab - they then look at thyroid hormone levels and TSH to decide whether they are blocking or stimulating.

And that is the most likely situation.

However, in the interest of confusing everyone, everywhere, TSHab are antibodies to TSH itself. They bind to TSH to form what is sometimes called macro-TSH. And the relevance of this is when they run a TSH test. Because macro-TSH lifts the reading hugely.

Most TSH testing has precautions built-in to prevent macro-TSH affecting the result, but some testing kits do get very wrong readings. No idea if any affected kits are still in use in the UK - I'd hope not, but you can never tell.

Plain ordinary TSH is how much TSH is in your blood.

Rod

[PinkNinja in reply to helvella]

Thanks for clearing that up! They need to be clearer. I don't like their naming convention

[Katkin1]

Phew - thanks for that both! Not sure I understand but will keep trying! Is it important that I try and understand the readings of both and post the results here (I know I have Hashi's) or shall I just go back to sleep?