TGAB and TPO antibodies - seem to fluctuate! - Thyroid UK

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TGAB and TPO antibodies - seem to fluctuate!


Hi group,

Thanks for taking the time to read this. I recently had results back with out of range TGAB and TSH with normal TPO, but following a re-test, was found to have normal TSH and high TPO (TGAB was not tested this time for some reason). I'm curious as to why my TPO antibodies have gone from fine to high in the space of a few weeks. Can anyone shed any light on this and the relationship between TGAB, TPO and TSH? (that's maybe an entire book right there!). As a result of the latest test my GP has put me on 50mg levothyroxine; I wasn't taking anything previously. Thank you xx

11 Replies

Welcome to the group Brianthecat23, I’m sure you will find that it is a source of useful information and support. I couldn’t have survived without it.

It would help people to comment if you put up any test results you have along with the lab ranges used.

How high was the TgAB? Extremely over-range TgAB means you have Hashi's. But, in any case, if your TPO antibodies are high just once, that means you have Hashi's.

Antibodies fluctuate all the time, that's the nature of the beast. It doesn't particularly mean anything, but once they say you have Hashi's, that's it, you have Hashi's for life. It doesn't go away, even if your antibodies go low.

TSH can fluctuate for many reasons, but one of them is because you have Hashi's - all levels will fluctuate. Presumably, your last TPO test was high enough to convince your doctor that the Hashi's has now done enough damage to make you hypo. And that's why he's put you on levo.

But, TSH can fluctuate throughout the day, so were these two test done at the same time of day? If not, you can't compare them.

TPO is highest early morning, and decreases throughout the day, and after eating. So, we always recommend people do all their tests at the same time, early morning, and fasting. Leave a 24 hour gap between your last dose of levo and the blood draw. Doctors don't know all this, so this is a patient to patient tip, and we don't discuss it with medical personnel.

When did your doctor tell you to go back for a retest? It should be six to eight weeks after the start of levo. Don't forget to ask for a print-out of your results. If you live in the UK, it is your legal right to have one. So, do ask for it. You need to keep your own records. And, on the back of the sheet, you can make notes about what you're taking and how you feel. You'll be thankful for those records in the future! :)

If you tested positive for TgAb you wouldn't need it testing again. Now you have raised TPO also, you have tested positive for Hashimoto's Autoimmune Thyroiditis. I think it's unlikely that NHS will test either again.

TSH is not one of the Thyroid Antibodies it's Thyroid Stimulating Hormone which is produced by the Pituitary Gland. If your Thyroid Gland is underworking and your Thyroxine (T4) is low then your Pituitary Gland will overwork and produce higher level of TSH. In my past experience doctors have tested TSH and T4 only. Problem with this is that, with Hashimoto's the regular tfts (Thyroid Function Tests ) results can fluctuate and fall within the 'normal ' range so not always reliable on their own. They can also fluctuate throughout different times of the day.

So your doctor has done well to test Antibodies too. Were you told you have Autoimmune Thyroiditis?

Ideally you should have FreeT3 and FreeT4 tested also.

Helpful to get some nutrients levels tested too in particular Vitamin D, B12, Folate and Ferritin because you may have some deficiencies that need treating with supplements (especially Vitamin D).

You should be retested (tfts ) in 6 to 8 weeks and have an increase in dose to 75mcg Levothyroxine. This should continue until stable. The 'normal ' range of TSH no longer applies once diagnosed with Hashimoto's and Hypothyroidism. The target therapeutic level is maximum of 2 (most people say max. of one). This is to protect your Pituitary Gland from over working.

Please give full results for further comment as mentioned.

"If you tested positive for Tg (TGAB) you wouldn't need it testing again."

Mary, why is this?

You may want to test again after a "within range" negative result but , if TPOAb raised, with a High TSH & low T4 (or FreeT4), indicating Hashimoto's, I don't think the NHS would test again.

Endocrinologist only tested my TPO Ab once as far as I know - result was 300. I'd already had the Ultrasound scan though which showed Thyroiditis. So tests results were conclusive.

I've no personal experience of having TgAb tested. But a raised (above normal range) result is a result isn't it?

It's the TSH, Free T3 and Free T4 that should be monitored , shouldn't they? Especially if symptoms aren't resolved or return.

Edit :


PS I think I may have caused confusion by putting Tg as well as TgAb. Sorry, I did , of course, mean the Antibodies (TgAb) and not Tg.

Thanks to all of you for your comments - really helpful.

To follow up on the exact figures, they were:

January 2019:

* Thyroid Stimulating Hormone (TSH) 7.83 mIU/L (0.27 - 4.3 mIU/L


Free Thyroxine (FT4) 14.9 pmol/L (12.0 - 23.0 pmol/L


Triiodothyronine (FT3) 4.22 pmol/L (3.1 - 6.8 pmol/L)

Anti-Thyroidperoxidase antibodies (11.2 kIU/L 0.0 - 34.0 kIU/L


Thyroxine (T4) 93.4 nmol/L (66.0 - 181.0 nmol/L)

* Anti-Thyroglobulin antibodies (TGAB) (244.0 kU/L 0.0 - 115.0 kU/L)

Vitamin D, Ferritin and Folate were all within normal. B12 couldn't be tested (my blood clotted apparently - it was a Thriva kit).

February 2019:

TSH 2.77 mU/L (0.35-5.00 mU/L)

Free Thyroxine (FT4) 12.6 pmol/L (9.0-21.0 pmol/L)

TPO antibodies U/mL

These were the only results in this test.

In 2015 my TSH was 6.2 in May and 5.4 in December. I haven't had the antibodies checked previously so have no idea what they were at that time, unfortunately.

I haven't been given an official diagnosis by my GP. She just thinks that these figures, combined with the fact that I've had a few periods of fatigue over the last few years, plus the fact that I might try for a baby soon, is reason to start me on levothyroxine.

I do live in the UK and am a bit of a maniac about keeping my records! But I will start monitoring how I feel now I'm on the meds. Great to know about the time of day. I have to go back in 6 weeks, so I'll make sure to not have my meds before I go, and to be fasting.

I asked about getting FT3 tested and my GP said that the lab was reluctant to do it and she didn't think it was necessary at this stage. Why would a lab be reluctant to do a test?!

Thanks for all your input - this is invaluable! :)

Why don't labs test FT3 ?? Cost I guess. They don't test for GPS only if requested by a Consultant. Sadly, NHS saving money comes before the health of Hypothyroid patients (opinion).

Presently GPs in our area can only get TSH tested. Annual TFTS check used to be TSH & T4, not even that now.

Antibodies results -

You haven't given your last TPO result .

Sorry, poor typing.

The TPO antibodies in Feb were 16.6 U/mL (<6)

That's a range I'm not familiar with but yes, if normal range is under 6 then a result of 16.6 is raised and therefore indicates Hashimoto's Autoimmune Thyroiditis. You also have the raised Thyroglobulin result.

You could ask your GP to send you for an Ultrasound scan of your Thyroid. You could also ask for a referal to an Endocrinologist. Not sure how far you'd get. But if you succeed then you should be able to get FT3 tested and FT4 - at least twice I would have thought. If they both improve you may be OK on Levothyroxine alone.

Thank you - I'll ask about a scan at my next appointment in 6 weeks. I had wondered about this. So I guess I do have Hashimotos and and hypothyroid? Will get GP to confirm this is her diagnosis. Thanks this has been so useful. :)

Hi again

You asked about the relationship between TgAb, TPOAb and TSH

As you'll know, Autoimmune Disease is when our immune system mistakenly attacks normal/healthy tissue.

Hashimoto's Autoimmune Thyroiditis is when it attacks the healthy tissue of the Thyroid Gland, rendering it Underactive. It was named after the Japanese Medical Scientist & Physician who discovered it : Dr Hakaru Hashimoto ( 5 May 1881 - 9 Jan 1934).

TSH (Thyroid Stimulating Hormone ) is the Pituitary Gland hormone. The Pituitary Gland acts as a 'messenger' to the Thyroid Gland.

If the Pituitary detects that there isn't enough Thyroid hormone in the blood it produces more TSH, prompting the Thyroid Gland to produce more Thyroid hormone.

The Antibodies :

TPO Ab (Thyroid Peroxidase Antibodies) I've read, are detected in 95% of people with Hashimoto's and around 70% of people with Graves.

Tg Ab (Thyroglobulin Antibodies ) detected in 80% of people with Hashimoto's and 50 - 70% of people with Graves.

There are other Thyroid Antibodies.

I don't know if the figures above are accurate but I found them on a website: article: THYROID DISEASE Understand Your Thyroid Blood Tests.

I found the information on the Thyroid hormones & tests easy to read and understand. So worth a read when you have time?

A very useful website is Thyroid UK. There is a list on there of 'Symptoms of Underactive Thyroid ' worth reading.

When we have a cold, sore throat or any infection, as our antibodies increase to fight it, then our Thyroid comes under more attack. I'd have recurrent respiratory tract infections and used to wonder why I'd always put on weight after an illness and take so long recovering from feeling tired and unwell.

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