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Sometimes the trickiest things are the ones that are not so obvious. If we can clearly see something, we can tackle it! It’s a lot harder when it’s more subtle. This can of course be the case when it comes to fertility issues. It turns out the Thyroid can be a subtle (or not so subtle) culprit or block when it comes to having a healthy baby. In fact, the latest stats show that as many as 1/5 women who experience sub fertility or miscarriage are impacted (9) In fact: Thyroid disorders are amongst the most prevalent medical conditions in women of reproductive age (9). Most are not being tested…

In this article we are going to look at why the Thyroid is so important to getting pregnant and to having a healthy pregnancy and baby. We are also going to consider signs you may be impacted and most important (as always) what you can do about it! 

The quick and dirty on why the Thyroid matters so much:

Thyroid hormones have a profound impact on reproduction and pregnancy. Dysfunction with it is implicated in a whole range of issues. Ranging from abnormal periods, lack of ovulation, miscarriage and even neurodevelopment issues in babies. (1)

In fact, it is the second most common endocrine (hormone) condition in women of childbearing age (2). It can also impact men. Albeit this is a bit less common.

Obvious or more subtle?

When you have a clear issue with your Thyroid you’re likely to experience a whole range of symptoms. This type of issue is less easy to miss! Check this to give you an idea:


However – you can also have no symptoms at all. You can have what is known as subclinical Thyroidism. Subclinical is basically where a condition is not severe enough to present strong (or any) symptoms. There is also debate about what constitutes ‘subclinical’ thyroid issues amongst medical bodies in different regions.

How can this impact me/why is it important?

If you do have an issue with your Thyroid it can impact conception/IVF success. It can also impact your periods, pregnancy and a baby’s brain development. It has also been linked to miscarriage. So it is pretty important! If you have any of the symptoms above – first port of call. Speak to your doctor and get tested. Pretty simple.

The good news!

This is relatively easy to treat, once you know what you’re dealing with. In a study of nearly 400 women struggling to get pregnant, nearly 77% conceived between 6 weeks and 1yr after having treatment. (2) So – if you’re concerned at all. Ask your doctor for a comprehensive Thyroid test. That includes testing for Thyroid Antibodies which are often the first sign of a potential Thyroid issue (9).

What about if you don’t have any Thyroid symptoms but you’re struggling to have a baby?

The subclinical form (once again this means no/mild symptoms) has also been shown to have an impact. Not only when it comes to getting pregnant, keeping a pregnancy (9), but also development of a baby. (2) So, even though symptoms may not be strong. It can still have an impact. It can also go undiagnosed for a while as a result. Obviously causing lots of potential trouble and anxiety. In certain areas like the UK the NICE guidelines (unlike those in Europe and the US) do not suggest testing as standard (9).

What happens when it is ‘subclinical’?

Typically this is where your peripheral thyroid hormone levels are within the normal range but your Thyroid Stimulating Hormone is elevated. (5) There are also wildly different estimates about how many people are impacted (which tells you something about it!) with a range of between 0.7% to 43% !! (5). There is also a differing definition of what an elevated TSH looks like. Some argue +4.0mIU/L and some say a level of above +2.5 is a potential flag (9).

The Endocrine Society in their latest research paper defined it as: ‘an abnormal serum thyroid stimulating hormone (TSH) with normal concentrations of free thyroxine. They may represent the earliest stages of thyroid dysfunction.’ (9).

The Endocrine Society Practise Guideline recommends investigation of a preconception TSH level above 2.5ml U/L for all sub-fertile women and women with a history of miscarriage or preterm birth. (9)

It can also look similar to Polycystic Ovarian Syndrome (PCOS) in some cases. (4) Not easy!

Autoimmunity is back! The other key element to the Thyroid story…

We know autoimmunity is on the rise globally. Thyroid Autoimmunity is essentially where the body produces antibodies against the thyroid. Attacking it essentially. Hashimoto’s is an example of this. It is the most prevalent autoimmune condition in women of fertile age. (5)

It can actually be the first sign that you may run into more significant Thyroid issues going forward and according to the Endocrine Society research it was ‘the factor associated most significantly with any degree of thyroid dysfunction’. (9).

’The presence of TPOAb (Thyroid Peroxidase Antibodies) increases the risk of progression to subclinical and overt thyroid disease in pregnancy’. (9)

However it is not often tested for and can impact conception and pregnancy. The stats suggest 3-5x higher risk for spontaneous miscarriage, placental abruption, preeclampsia, preterm delivery and loss. (2) It has also been linked to unexplained infertility, sub fertility, recurrent miscarriage and even potentially impacting the quality of eggs. Yikes:

In fact, anti thyroid hormones are found in as many as 5-10% of women of reproductive age. (4, 9)

What about for guys? Can the Thyroid impact sperm?

Yes. Although it is less common, recent research has shown that there is a relationship between Thyroid, testis and sperm. With hyperthyroidism typically leading to low semen volume/motility and morphology (shape). Hypothyroidism leading to potential problems with morphology. (3)

What causes problems with the Thyroid?

The potential causes of mild thyroid dysfunction or thyroid autoimmunity are not well understood. It can also go undiagnosed when there are not typical symptoms. Particularly as in some countries like the UK it is not a recommended screen. However, even mild forms can have an impact. (5)

So what can you do?

The good news is a few things!

First port of call if you have been struggling to get pregnant for any length of time is to speak to your doctor. Ask to have your Thyroid Stimulating Hormone tested and ask for your level. If it is above 2.5 ml U/L you may wish to push for further investigation. Also ask for a test for anti thyroid antibodies (TPOAb). We always believe more knowledge about your own body is power!

Other things to support the Thyroid:

As always there are a few things you can do to support your body and healthy hormonal balance:

Vitamin D and your Thyroid:

We know that autoimmune conditions are on the rise these days. There has been some research connecting this to Vitamin D. Specifically not having enough. (2) Antibodies to the thyroid (which is an autoimmune condition) is something that can impact fertility/pregnancy so anything we can do to support a healthy immune system is helpful.

Is this conclusive? No, but evidence is gathering of the positive impact Vitamin D has on the immune system and it is certainly a tool in the fight against autoimmunity. (4) Having enough is good for many issues. Once again, if you’re concerned, get it checked.

When it comes to  immunity: the gut microbiome is also important:

The major heartland of your immune system.


In a nutshell however, it is used by your Thyroid to make Thyroid hormones. So, you need enough of it!

In fact, during pregnancy a woman’s requirement goes from 150 to 250 µg/day) to ensure adequate supplies are given to the growing baby. (7)

Like most things though. It’s Goldilocks. We don’t want to go overboard with too much – also not what you want. It’s about getting it just right. As with everything – speak to your doctor about it if you think you may need support.

Things that can hurt our Thyroids?

The Thyroid is pretty sensitive to environmental toxins. Research has linked trouble to our old enemy pesticides – particularly Glyphosate. One of the leading experts in how Glyphosate impacts developing children (Stephanie Seneff at MIT et al) argues that there is significant evidence showing that Glyphosate impacts (lowers) maternal production of Thyroid Stimulating Hormone.

Secondly: Bromine: has been found to block iodine rich foods from being useful and absorbed to some extent. Where do you find Bromine? It is found in some industrially processed and packaged foods – yet another reason to avoid and to make your own!

Where can I find more Iodine?

Well – food is not generally high in iodine, that being said there are some foods which have a higher concentration than others:

  • Sea Vegetables: think Kelp/Seaweed
  • Cranberries
  • Plain Yogurt
  • Strawberries
  • Potato
  • Seafood (remember to go low down the food chain to avoid mercury)
  • Eggs
  • Green Peas
  • Cheese
  • Wild Caught Cod
  • Bananas

How much do we actually need?

Of course we now have iodised salt – but – against this is the need to keep salt intake at a minimum during pregnancy and breastfeeding. In Europe, it is recommended that multivitamins are given to pregnant and breastfeeding mothers to reach the 250 microgram requirement. It is worth checking if your pregnancy/breastfeeding supplement has the required amount. If not and if in doubt discuss with your doctor.

Stress and other hormonal imbalances:

Imbalanced estrogen ie. too much. Plus BPA (found in certain plastics), other environmental toxicants (Fluoride, heavy metals etc) and stress have all been linked to knocking our thyroids. Finally: Avoiding other hormone disruptors like Phthalates (found in added fragrance products for example) are a good idea.

Clean living and reducing physical and mental stress is another way to go. Makes sense!

Conclusion/Action points to all this?

Becoming an expert in your own body can be really powerful. If you’re noticing symptoms above or you’ve been trying to have a baby for a while with not much luck, this could well be worth investigating. Speak to your doctor about having a comprehensive test (including TSH/anti thyroid antibodies).

Aside from that it is all the same message. It’s not rocket science. Avoid nasties where you can, whole unprocessed food, prioritising gut health and lots of Vitamin D!


1) Prevalence of hypothyroidism in infertile women and evaluation of response of treatment on infertility: International Journal of Applied Basic Medical Research: 2012 Jan-Jun: 2(1): 17-19 

2) Thyroid dysfunction and thyroid autoimmunity in euthyroid women in achieving fertility: European Review for Medical and Pharmacological Sciences: 2015: 19(6): 977-987

3) Thyroid dysfunction and semen quality: International Journal of Immunopathology and Pharmacology. 2018 Mar-Dec. 

4) Thyroid disorders in polycystic ovary syndrome: European Review for Medical and Pharmacological Sciences: 2017: 21(2): 346-360

5) Association of Thyroid Function and Autoimmunity with Ovarian Reserve in Women seeking Infertility Care. Thyroid. 2018. Oct: 28(10): 1349

6) Thyroid Dysfunction and subfertility: Clinical and Experimental Reproductive Medicine. 2015 Dec: 42(4): 131-135 


8) Samsel A, Seneff S: Glyphosate,. Pathways to modern diseases III: Manganese, neurological diseases and associated pathologies. Surgical Neurology International: 2015: 6:45

9) Dhillon-Smith R, Tobias A, Smith P, Middleton LJ: The prevalence of thyroid dysfunction and autoimmunity in women with history of miscarriage or sub fertility: The Journal of Clinical Endocrinology & Metabolism: June 2020.


This article is for informational purposes only. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The information on this website has been developed following years of personal research and from referenced and sourced medical research. Before making any changes we strongly recommend you consult a healthcare professional before you begin.