Thyroid Tests

Unsure if you need a Thyroid Test?

Check the Thyroid Problems factsheet out here.

Thyroid Testing Summary

I’d love to tell you there is one thyroid test that does everything. But there isn’t. The best overall thyroid markers test is the Genova Thyroid Plus (PHC) and I love the easy report it gives. If you are having problems, for a really comprehensive look at everything, I would combine the Thyroid Plus with a D102 (RG), a Urine Halides Loading (RG) and a Genova Nutrient and Toxic Elements Test (PHC).

IMPORTANT: If using Genova or Invivo, please send me an email or forward me the confirmation so I know where to send results when they come in. If you don’t email me, I can’t send them! For Biolab, you can’t order direct, so use a lab test request form here. I will confirm price and invoice you. All results will be released after payment is received.

Best Overall Thyroid Test

My favourite overall thyroid test is the Genova Thyroid Plus (PHC). I like it because it looks for the usual TSH, free T4, free T3 etc, but also gives an idea of how much inactive reverse T3 you are making, shows up conversion problems that might be related to selenium or iodine deficiency (surprisingly common this latter one, measures the main autoimmune antibodies. With all that info, you can make a start on seeing what is going wrong, what further investigations might be useful and how to treat effectively.

Bloodspot Test

There is also a blood spot and dried urine thyroid test from ZRT which might make life easier for those of you who don’t want to do a full blood test. The ZRT Comprehensive Thyroid Panel with Elements (RG) has most of the usual markers I would look for – although only one of the autoimmune antibodies and no Reverse T3 – but it does include thyroid elements like iodine, selenium, arsenic and bromine. I rather liked the report they give too.

Weight Issues

If your issue is with weight, you might choose the ZRT Weight Management with Thyroid (RG). This does the most common thyroid markers but lots of other elements related to weight issues, including insulin resistance, a diabetes check, hormones and adrenal function.

Genetic Testing – D102

There are many genetic variants that can affect how thyroid hormones are metabolised and used in the body. Sometimes, if you can’t seem to get your thyroid to sort itself out with usual measures, it can pay to look for genetic clues. The simplest and best known is the DI02 Deiodinase gene. Some people have a fault on the gene that controls T3 delivery to the brain and these are often people who don’t do well on normal thyroxine treatment and who do much better in combination with T3. You can test this with the DI02 Deiodinase test (RG).

Conversion Problems – Iodine and Selenium

More often than not, I find that people are making enough thyroid hormone but not converting it properly into the active hormone T3, or they are converting too much of it into the inactive hormone Reverse T3. These conversions are utterly dependent upon iodine and selenium levels.

Iodine and the thyroid

With iodine issues, the most suspect pattern is if T4 is low with normal or high T3.

You can test for iodine itself using the Urine Iodine test (RG), but I prefer to use a Urine Iodine Loading test (RG) which shows you how you are actually metabolising it. Is there enough left in your system to do it’s job for your thyroid? Even better, you can test Urine Halides Loading (RG) where you can see if the iodine is OK, but also if levels of bromine and flourine are blocking the iodine.

If you do an iodine loading test, this info might help:

If the body has sufficient iodine, at least 90 per cent will be excreted in the urine. In iodine deficiency, however, the body will hold on to some of the iodine to compensate for the deficiency. The more iodine that remains in the body, the more a person is iodine deficient and needs to begin supplementation.

After determining an iodine deficiency, supplementation should begin gradually, because iodine mobilizes toxic metals and goitrogenic substances from their storage sites potentially increasing peripheral levels high enough to cause symptoms.

Iodine therapy is usually using 50 mg/day. The body becomes iodine sufficient in about three months. Testing should be repeated every three to four months to monitor proper iodine doses.

Iodine Treatment (discuss with your health professional)

The usual advice is to use something like Iodine Complex 12.5mg tablets and start with 1 and build up over 3-4 weeks to 50mg per day (4 tablets).  Then, maintain at 50mg for 3 months and re-test to check the level is coming up nicely, or tweak if not. 

If you are TGF/grain free, you would do better to use Biotics Iodizyme, which is the same strength as Iodoral at 12.5mg per tablet.

Alternatively, you could use Lugol’s Iodine solution, which is often used on the skin.  You can get it in two strengths – 7% and 15% – be led by your health professional as to which you need.

Note that Iodine is best for oestrogenic activity eg. on breast tissue etc.  For the thyroid, you need one that has iodide in it (that’s just iodine complexed to potassium or sodium really) as per the ones above.

Iodine/Iodide is best taken in the day as it can be quite stimulating, and it is best absorbed with Vitamin C and other minerals, which act as co-factors.

Re-test after 3 months because too much iodine can actually inhibit thyroid function so you want to know you’re not going too high.

This Halides Loading test can also give you an indication of symporter iodine transport problems. Some people can’t transport the iodine to the receptors properly and, quite commonly, this is because the other halides – bromine and flourine – that compete with it are too high. You can read a technical, if useful, factsheet on Symporter Transport Thyroid Problems here.

Selenium and the thyroid

Selenium is specifically needed to convert the inactive T4 into the active T3. If you don’t have enough selenium in the right place at the right time, it will impact your T3 levels. The most usual pattern to suspect is low T3 with normal TSH and T4.

The simple approach is to ensure enough selenium as a separate supplement, as part of your multi or a few Brazil nuts a day. You can check your levels and I most often recommend checking all mineral levels if you can because one mineral deficiency can usually mean others are out too. For that, I would use the Genova Nutrient and Toxic Elements (PHC) because it also looks for heavy metals, which we know can also have a major impact on the thyroid.

Incidentally, if mercury looks high on that, follow up with a Quicksilver Mercury Tri-Test (RG) to see what kind of mercury it is and if it needs treating.

Phew there’s a lot there, sorry; it’s a complex subject this one. Here’s my summary to remind you:

Thyroid Testing Summary

I’d love to tell you there is one thyroid test that does everything. But there isn’t. The best overall thyroid markers test is the Genova Thyroid Plus (PHC) and I love the easy report it gives. If you are having problems, for a really comprehensive look at everything, I would combine the Thyroid Plus with a D102 (RG), a Urine Halides Loading (RG) and a Genova Nutrient and Toxic Elements Test (PHC).

Testing Tips….

Many people will test whilst they are on long-term thyroid meds eg. thyroxine to see how they are on it/is it enough etc? If you are on something like Armour, again you can test on it – just take your usual dose after the blood draw – or, if you are stopping either (with your health professional’s assent, of course), then the lab advises you would need to wait 90-100 days for it to come out of your system and get a clear result.

Iodine and Halides Loading tips…


The lab will then drop-ship it to the US lab for you.

How do I do the test?

You take a urine sample when you get up in the morning, put it in the ‘Pre’ vial, label that and then take your loading dose of 50mg of Iodoral; that’s all 4 tablets together (unless your health professional advises otherwise, of course). From then on, you collect your urine every time you go for the next 24 hours or until you fill the 4 litre jug. You then shake the jug to mix the urine up a bit, write down the total volume of urine collected in the post section on the form (should be max 4000ml obviously but might be under that), then take a sample and put it in the ‘post’ vial, labelling it correctly. Ignore the Excess volume bit of the form; it’s just confusing and you don’t need it. You then package your samples up, following the instructions and packaging given in your kit. Make sure your form is filled in completely – especially the pre and post urine volume amounts which are crucial otherwise they can’t calculate your results properly – and put it with the samples (otherwise it will be rejected) and Bob’s your Uncle.

Will I get iodine tablets in the kit?

Yes, 4 x 12.5mg Iodoral tablets for the challenge test are included with your kit.

What if I collect more than 4000ml of urine over the 24 hours?

It does say to stop at 4000ml so you just fill the jug up to the fill line and then discard the rest.

Do I have to avoid anything?

With this test, you need to avoid any iodine supplements and iodine rich foods like seafood, kelp, fish (see the instructions in the kit) for 48 hours before the test. You don’t need to stop any other supplements but I often say if unsure stop all supplements for 48 hours to be sure.

I am on thyroxine/Armour, can I still do the test?

The lab advises that thyroxine and other thyroid boosters like Armour should not interfere with results but you need to be careful of over-stimulating your thyroid and be led by your health professional. If you have autoimmune thyroiditis or hyperthyroidism, for example, taking the iodine could cause a thyroid storm so do please talk to your health professional to be safe. I have never known it, but that’s what the lab advises. If taking the test, it is best to take the loading dose well away from your thyroxine or Armour.

I am on other meds, can I still do the test?

Probably. Here is a list of interactions of meds with iodine. Check with your health professional – and often a local pharmacist can be very helpful.

I urinate a lot, will I have to drink less on the day of the test?

There is an option to take a representative sample of your urine anyway. You measure the total volume first and write that on the form. I would trial a normal day and measure what you usually pass and cut down if it is beyond the reference range given on the test instructions.

I see the test measures creatinine. I do a lot of exercise which I read raises creatinine. Does this matter?

The creatinine is only used as a baseline to measure urine concentration levels so they can calculate the retention levels etc. Exercise, raised or low creatinine levels serve no diagnostic purpose here and therefore won’t affect your results.

Does the urine sample have to be frozen?

No, not even if sending from Europe.

Do I have to take the loading dose with food?

It’s always best to take supplements with food so I would have it with a bit of a snack, although it doesn’t matter for your test results.

I have heard that I could have a Symporter transport problem with iodine. Can you test for that?

We don’t do an actual Symporter test as it is very unwieldy to do and hard to get done in the UK. However, we do know that one of the main causes of a symporter issue is high halides, so do the Halides Loading test first and, if those are high, you have your answer. If the halides are low, you’ve ruled that cause out, but there are others including genetic defects, goitrogens, some pesticides and oxidative stress, to name a few. There is useful, if pretty technical, factsheet here for you on Symporter transport testing and treatment.

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