Today is the second post in my thyroid series where I will cover everything you need to know about thyroid testing: from what tests are currently offered to what you actually need to be looking at (spoiler: it’s much more than you’re being told), and why the difference in what is considered ‘normal’ and ‘optimal’ is so important for fertility, pregnancy and postnatal health.

In the first post in this thyroid series I covered the basics about your thyroid function. If you haven’t seen that already, I’d suggest you go back and read it HERE as it gives you the background to this post and the hormones I will be speaking about.

Standard thyroid testing

When you visit your GP in the UK you’ll currently only be offered a blood test for two thyroid hormones: TSH (Thyroid Stimulating Hormone) and T4 (Thyroxine) but as you know from my last post there are many more hormones involved in thyroid function. Importantly it’s the interplay between them all which dictate whether your thyroid is running as it should be.

Think of your hormones as an orchestra, we don’t need one dominating the ‘melody’

Your hormones run in delicate balance with one another. Think of them as an orchestra, with each one having a unique function and timing but we don’t need one dominating the ‘melody’; they must work together. So when we only check on the strings and percussion, for example, you don’t hear the whole piece of music. It’s the same with thyroid testing, if you only check one or two markers you can’t really understand the totality of the situation.

There are eight markers that ideally we should be looking at:

  • TSH (which is made in the brain and tells the thyroid to do something)
  • T3 (Triiodothyronine) the active thyroid hormone, in both free and bound states
  • T4 (mostly ineffective but gets converted into T3 or sometimes reverse T3 in both free and bound states)
  • Reverse T3 (the inactive form of T3; quantity matters as too much affects T3 levels)
  • TPO (Thyroid Peroxidase Antibody) – a marker of autoimmune disease
  • TGA (Thyroglobulin antibodies) – a marker of autoimmune disease

It’s worth knowing that hormones come in both ‘free’ and ‘bound’ states in the body. Free means whether the hormones is circulating freely in the blood and available to use or whether it’s bound (attached) to a protein and would need to be decoupled before the body can utilise it.

When your thyroid tests come back normal but you don’t feel fine

Hopefully you’re starting to see why having a greater understanding of all of your thyroid’s hormone levels would be of benefit? To emphasise how important this can be when you’re trying to conceive I’ve recently worked with a fertility client who sadly experienced multiple miscarriages in 2021 and couldn’t understand what was causing them. She ate a healthy diet and exercised, she was even taking prenatal vitamins and had asked her GP for a thyroid blood test.

Her tests had come back as ‘fine’ from her doctor but I suspected that some of her symptoms on top of the miscarriages were indicating the her thyroid was struggling. She was feeling tired on waking every day but her energy would increase as the day went on; she was always feeling cold and her periods had become heavier and more painful in recent months. We sent her for a fully comprehensive thyroid test with some additional vitamin and hormone markers that support the thyroid to see what was going on.

When her results came back she had borderline underactive thyroid with some autoimmune elements present which needed addressing. After another two months of targeted thyroid support using food, exercise and stress reduction I’m happy to report she’s now 16 weeks pregnant and baby is thriving.

What normal vs optimal thyroid tests results look like

In addition to not testing sufficient markers for thyroid health, the standard reference ranges are too wide in scope. Reference ranges are the set of markers which your blood tests would ideally fall between to determine whether there was anything wrong. When these ranges were originally set they were calcuated using an average of results (the mean) and the differences in those averages (standard deviation) collected from a large population data set. Frustratingly they aren’t regularly updated and are set for disease prevention not for helping you get pregnant or recover after birth.

This means that often your results come back ‘within range’ but you still feel unwell and know there is something wrong. You could in fact have sub-optimal thyroid levels – either too high or too low – which are impacting your health.

Standard ranges in the UK (which can vary between lab) are currently:

  • TSH: 0.27 – 4.2 miu/L
  • Free T3: 3.2 – 6.8 pmol/L
  • Free T4: 12-22 pmol/L
  • Thyroglobulin antibodies: 0-115 IU/ml⠀⠀⠀⠀
  • Thyroid peroxidase antibodies: 0-34 IU/ml⠀⠀⠀

And if we compare these with optimal ranges:

  • TSH: 1.5-2 miu/L
  • Free T3: 4.5 – 6.0 pmol/L
  • Free T4: 16-20 pmol/L
  • Total T4: 77.2 -154.4 nmol/L⠀⠀
  • Total T3: 1.54 – 3.53 nmol/L
  • Reverse T3: <20ng/dL
  • Thyroglobulin antibodies: 21kIU/L⠀⠀⠀
  • Thyroid peroxidase antibodies: <15kIU/L

The differences are huge. In clinic when I’ve helped to bring my client’s markers back within the optimal ranges they see huge improvements in how they are feeling.

Your results could come back ‘within range’ but you could still have sub-optimal thyroid levels

How undiagnosed sub-optimal thyroid function could be affecting your health

I’ll talk you through another client example to demonstrate how this might be affecting your health in real time. My post natal client came to me for weight loss and breast milk supply support. She had a genetic history of an underactive thyroid in her family (which can be important) and had been feeling really low about her post baby body. After adjusting her diet, working on improving her sleep and stress levels (all factors for sustainable weight loss) we turned to her blood tests.

As with my fertility client she had been told everything was normal and to come back in three months if her symptoms persisted. She had requested the tests initially because she was feeling tired all of the time. We ordered her a comprehensive thyroid panel and when the results came in she also had an underactive thyroid with autoimmune elements, both of which can make it more difficult to lose weight. After sending her back to her GP for medication and re-adjusting her diet over a number of weeks she’s now happily losing a steady 2-3lbs a week and feeling more energised and happier as a result.

The bigger picture

As I wrap up this post it’s important to say that every person is biochemically and genetically unique. As a practitioner I have to take this into account and make sure to read client’s test results alongside their symptoms and then make decisions about their health based on all of that information. Health is like a jigsaw puzzle and we can’t only focus in on one element (test results) without zooming out to see the whole picture. Getting to the root cause of what’s causing your thyroid imbalance alongside making professionally directed diet and lifestyle changes can really transform some people’s health; I’ve seen it first hand.

If you have enjoyed this post and want to see more content from me then you can sign up to my community using the link on the homepage and if you know someone who might benefit from reading this then please share the love, it’s always appreciated.

And if this post has made you think now is the right time for some personalised support to help manage your thyroid why not book in for a free support session HERE. I’m looking forward to hearing from you.