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The relationship between thyroid & fertility (& what you can do)


If you’re trying to get pregnant, or starting to look into your fertility, you may begin hearing a lot about your ‘thyroid’. This could be the first time you’ve heard of the word, or you might have a longstanding relationship with thyroid issues (which are becoming a real pain in the a*s now that you’re trying to conceive).

So exactly what is it, and how can thyroid problems cause fertility problems?

What’s a ‘thyroid’ anyway?

That’ll be a helpful place to start.

The thyroid gland is a butterfly-shaped organ at the front of your neck, just below your voice box. This inconspicuous little gland is important for producing and regulating hormones in your body – more specifically, the thyroid hormones triiodothyronine (T3) and thyroxine (T4). These T’s play a big role in ovulation, preventing miscarriage, and promoting your baby’s development. 

So what’s the relationship between the thyroid and fertility? (The neck seems far removed from your ‘down there’ reproductive area, right?)

As you’ll know, bodies go rogue sometimes. In some people, the thyroid starts overproducing or underproducing hormones. It’s known as ‘thyroid dysfunction’ or ‘thyroid disease’, and can be brought on by iodine deficiency or autoimmune disorders.

The signs of an overactive or underactive thyroid may be subtle. You may not even notice it. But the thyroid’s effect on fertility can be a big indicator that something’s off with your hormones.

How can thyroid affect fertility?

Hormones play a big part in triggering the changes that need to happen in our bodies to make babies. (They’re also the a*sholes responsible for making us feel so sick in early pregnancy.)

So if out-of-whack hormones affect your body’s ability to do what it needs to do, can thyroid problems cause fertility problems? You betcha.

When your thyroid hormones are playing up, you might experience difficulties with ovulation, abnormal menstruation cycles, and a higher risk of miscarriage. Let’s look at what can go wrong with thyroid and fertility.

Underactive thyroid and fertility problems

When your thyroid doesn’t produce enough T3 and T4, it’s known as ‘hypothyroidism’. 

Symptoms of hypothyroidism might include:

  • Fatigue
  • Low energy
  • Weight gain
  • Sensitivity to the cold
  • Depression
  • Dry skin
  • Menstrual cycle irregularities (usually heavier, less frequent periods)
  • Difficulty conceiving.

Underactive thyroid fertility problems could be related to unpredictable cycles making it tough to bang at the right time. But also, thyroid disease can interrupt the production of other vital reproductive hormones, such as follicle-stimulating hormone (FSH) and luteinising hormone (LH).  

If your thyroid is not producing enough hormones, you’ll need to get more of those hormones in your system to fall pregnant.

Overactive thyroid and fertility problems

So can an overactive thyroid affect fertility too? Yes, when there’s too much thyroid hormone in your body, it’s known as ‘hyperthyroidism’.

Symptoms of hyperthyroidism can include:

  • Anxiety
  • Tremors
  • Increased heart rate
  • Weight loss
  • Sensitivity to heat
  • Brittle hair or hair loss
  • Enlarged thyroid gland
  • Lack of libido (which helps for getting pregnant amiright?)
  • Menstrual cycle irregularities, or cycles coming to a stop altogether.

It’s not impossible to fall pregnant with hyperthyroidism, but it can be more challenging if your periods are all over the place. 

In this case, you’ll need to slow down the production of thyroid hormones in your body to get pregnant.

Thyroid antibodies and fertility problems

Thyroid antibodies will be produced if your thyroid gland is accidentally attacked by your immune system. (Yeah, seriously, the body does that sometimes.) This is generally caused by an autoimmune disease. 

Conditions like Type 1 Diabetes or Hashimoto’s Disease could be the culprit, so if you have an autoimmune disease like this (or if there’s a history of it in your family), your doctor will probably test you for thyroid antibodies. 

Thyroid antibodies and fertility also have another unfortunate association. Antibodies increase the risk of pregnancy loss by four times, so if you experience recurrent miscarriages, this will be one of the areas your fertility specialist will check out.

Testing for thyroid and fertility issues

Awkwardly, a lot of the symptoms of thyroid complications are sort of vague and similar to other health issues. So… How would a doctor diagnose you?

They might run a few tests:

  • A blood test – A blood test can pick up thyroid antibodies, as well as irregular thyroid hormone levels to confirm if you’re experiencing thyroid dysfunction.

  • A physical examination – Your doctor may feel your thyroid gland from the outside to check for lumps, nodules or swelling.

  • Imaging tests – Your doctor may also request an ultrasound of your thyroid area to check for growths or other weird stuff.

There’s some debate about whether thyroid testing should be done on all pregnant women, but in Australia it’s not the norm. This is largely because studies have shown that while routine testing increases thyroid dysfunction diagnosis, it doesn’t actually affect birth outcomes or reduce the rate of pregnancy complications

But anyway, we’re here to talk about getting pregnant in the first place, which can be the hardest part.

What are ideal thyroid levels for fertility?

You CAN get pregnant even if your thyroid is causing you issues. The key is to work with your doctor to achieve optimal thyroid levels for fertility.

Normally, thyroid stimulating hormone (TSH) levels fall between 0.5 to 4.5. Higher levels are associated with hyperthyroidism, and lower levels are associated with hypothyroidism. However, recent studies suggest that TSH should be no higher than 2.5 when trying to conceive, and 3.0 during pregnancy. 

Chat to your doctor about what they recommend for you. And heads up: Your iodine levels directly impact the production of thyroid hormones in your body too. So Doc might prescribe a supplement if you’re one of the 62 per cent of women with lower than recommended iodine.

Does thyroid affect male fertility?

Sure does! If your partner/sperm donor has thyroid problems, that can affect your chances of falling pregnant too.

An under or overactive thyroid can affect male fertility by:

  • Reducing sperm volume and movement
  • Causing sperm defects
  • Lowering libido
  • Causing erection issues
  • Lowering male fertility hormones.

If you’re knee-deep in fertility testing, a blood test for your partner should pick up on their thyroid issues.

How to treat thyroid fertility issues

If your doctor suspects that your thyroid might be causing infertility, they’ll advise on the best form of treatment to get your hormone levels balanced out. It can be done! (*sighs with relief*)

Thyroid fertility treatment may include:

  • Medication – An underactive thyroid can generally be treated with thyroid replacement medication, such as levothyroxine. Anti-thyroid drugs like methimazole and propylthiouracil might be prescribed to treat hyperthyroidism.

  • Surgery – Another treatment option for more severe hyperthyroidism is a thyroidectomy, which involves removing the thyroid gland altogether. You can live without your thyroid gland, but you would need to take thyroid replacement medication for the rest of your life.

  • Investigating other, related health conditions – Thyroid disease often goes hand-in-hand with other hormone-related conditions, like polycystic ovary syndrome (PCOS). (They’re like besties.) This might require additional treatment, but the good news is it’s still possible to fall pregnant and deliver a healthy, cute AF baby if you’re diagnosed with one or both conditions.


OK. So. We hope this long-winded explanation has helped you wrap your head around how thyroid and fertility are related. If you’re stressing out about your thyroid situation, know that you’re not alone. With the right treatment, many women with hormonal imbalances manage to have a successful pregnancy. And you can be one of ‘em!

The information in this article does not replace medical advice. If you have any concerns about your thyroid or fertility, speak to your doctor or ob-gyn for personalised advice.



Read next: How to talk to friends and family about your infertility

Fertility Centers of Illinois, Ask the Doctor: 10 Questions About Thyroid and Infertility

Create Fertility, Hyperthyroidism and fertility

Australian Government Department of Health, Thyroid dysfunction

Cleveland Clinic, Thyroid Disease

Verywell Health, Fertility and Pregnancy Challenges With Thyroid Disease

Tennessee Fertility Institute, Thyroid Disease and Infertility

Patient, How an underactive thyroid affects fertility

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