TSH Receptor Antibodies - Could someone explain me what they are?

[Nathalie70]

Hello,

I was diagnosed with an over-active thyroid in September 2012 and Graves. I've been off Carbimazole for 2 months now and so far, my thyroid has not become over-active again.

My endo tested my TSH Receptor Antibodies a couple of weeks ago. The results are:

1.18 IU/L - range 1.5-1.75

Does someone have more information about his specific blood test and those results? I couldn't find anything interesting online and my endo is on sick leave.

Thanks a lot and take care!

[helvella Administrator]

They are commonly referred to by multiple names and abbreviations - so finding can be difficult. TRab is quite common.

There are at least three varieties which are not distinguishable by the usual tests. The first is the blocking antibody which can stop the TSH receptor from working properly. The second is the stimulating antibody which attaches in much the same was as the blocking antibody but triggers the receptor in much the same way as TSH itself. Trouble is, it stimulates too well and results in hyperthyroidism - the fundamental mechanism of Graves' hyperthyroidism. And antibodies which neither block nor stimulate. (There may be sub-divisions but if there are, no-one gets tests which show them.)

The standard test identifies the numbers of TSH receptor antibodies but not whether they are blocking or stimulating. That is assumed from the thyroid hormone tests and clinical signs and symptoms.

Rod

[Nathalie70]

Thanks a lot Rod for your detailed explanations. I had my endo this morning on the phone and he told me that it means my Graves is declining or I may self-healing it, my TSH and T4 being normal and having no clinical symptoms. That's good news

[helvella Administrator in reply to Nathalie70]

Managed to miss that the third type seems to have neither blocking nor stimulating effects!

[jessi4]

Are the Antibodies affected by the medication? I have only just done TRAB blood test ( it was missed off last antibody blood test, but the one done was positive) already on block and replace, and wondering if it should have been done before any medication started

[Nathalie70]

I guess it should have been done before the treatment started to see if the result improves or not. It wasn't done in my case, it was done only when the treatment was stopped. I actually left the NHS and went private, hence this new test. My endo thinks the test would have been negative before the start of the treatment as it's negative for 50% persons having Graves. I understand it's a matter of controversy among the endos as some suggest that if the antibodies are negative, it's not a Graves.

In my case, I was hyper for 3 years before being diagnosed, my symptoms being very confusing and as soon as I started carbi and only 15mg, my TSH reappeared and my T4 went back to normal. All these suggest an absence of Graves or a minor one, which is confirmed by the blood test.