Our thyroid gland secretes thyroid hormones which impact our metabolic rate. These hormones then impact our fertility hormones. With around 1 in 20 people having some type of thyroid condition, you should know what symptoms to look for and how to optimise your thyroid health before you start trying to conceive.  Check out today’s blog to learn more!

Thyroid and fertility

When your thyroid gland produces too much of the hormone, thyroxine, it’s called hyperthyroidism. The most common cause of hyperthyroidism is a condition called Grave’s disease. Grave’s disease is an auto-immune condition, which means that your body decides that healthy cells are foreign, and it attacks those healthy cells. When your thyroid gland produces too much thyroxine, it can impact fertility hormones such as estrogen and progesterone to cause irregular ovulation and increased rates of miscarriage.

Conversely, when the body doesn’t produce enough thyroxine, it’s called hypothyroidism. Hypothyroidism can also cause irregular periods and problems ovulating.

Since both hypo and hyper-thyroidism can have a significant impact on your fertility, it’s important to make sure that your doctor has checked your thyroid hormone levels with a blood test. Depending upon the levels of your hormones, you may require some medications, or even surgery in extreme cases, to regulate your thyroid production, but there is a lot that you can achieve with dietary changes too.

Let’s take a look…


You may have heard that a nutrient called iodine is important for your fertility…. The reason for this is because iodine composes an important part of your thyroid hormones.

The thyroid gland produces two primary hormones – thyroxine (also referred to as T4) and tri-iodothyronine (also referred to as T3). The numbers 3 and 4 refer to the number of atoms of iodine in the hormones. Iodine is essential for the production of thyroid hormones and humans need about 150 micrograms each day. Iodine is found in a wide range of nutritious foods as it comes from the soil and sea.  Seafood and fish is one of the best sources of iodine, so if you’re meeting the recommended requirements of two to three serves of fish per week, plenty of fresh fruit and vegetables, some wholegrains and 3 serves dairy per day, then you’ll most likely be meeting your iodine requirements.  But, if your diet is high in processed foods or you have hypothyroidism, then there’s a good chance you won’t be meeting your requirements, in which case you may need to take an iodine supplement before you conceive. But please note, that iodine supplements can be dangerous for women who have Grave’s disease, so please check with your health care professional first.


Goitrins can interfere with the synthesis of thyroid hormones, although this usually only occurs when coupled with an iodine deficiency.  Goitrins are found in cruciferous vegetables, like broccoli, cauliflower and cabbage, soy and a grain called millet.

Research has found that people who take excessive amounts of soy products, usually via supplements, are more likely to have hyperthyroidism. Furthermore, there is some suggestion that people who have hypothyroidism and are taking thyroxine medications should avoid taking high amounts of soy. Please note that this doesn’t mean that you need to avoid soy foods altogether. It’s fine to have one or two serves of soy foods, like tofu, soy milk or faux meat each day, but I’d recommend not taking it at the same time that you take your medication, instead wait an hour or two, and avoid soy capsules.

It’s also important to note that the goitrogenic effect of cruciferous vegetables is erased when they are cooked, so don’t let this be an excuse not to eat your broccoli! You know that it’s good for you!


If you are prescribed medications for your thyroid it’s also wise to note that you should take these at a different time to your nutritional supplements. Nutritional supplements can impair your body’s ability to absorb the medication properly, so try to take them at least four hours apart.

Vitamin D

Vitamin D deficiency is common, and it is even more common in people with hypothyroidism. In fact one study found that 90% of people with hypothyroidism had a vitamin D deficiency. Researchers aren’t yet clear if vitamin D deficiency increases the risk of hypothyroidism, or hypothyroidism increases the risk of vitamin D deficiency, but either way, if you have hypothyroidism, its worth having your vitamin D levels checked, especially before you conceive.

Vitamin D is also important for women with hyperthyroidism, as hyperthyroidism, particularly Grave’s disease has been found to cause bone loss, and vitamin D is essential for healthy bones.


Finally, I also want to discuss weight. Hypothyroidism can make it difficult to lose weight as it slows down your body’s metabolic rate. If you have hypothyroidism, try to focus on eating well rather than the number on the scales until your thyroid hormones are back in the normal range.

It is recommended that you work on your metabolism by increasing your muscle mass and eating small regular meals. You can increase your muscle mass by ensuring that you consume adequate protein in your diet and by participating in regular exercise. Furthermore, exercise elevates the effectiveness of thyroxine in the bloodstream by approximately 30%, so exercising is an excellent way to achieve and maintain weight loss for someone with hypothyroidism.

Increasing your muscle mass is also important for women with hyperthyroidism, as high levels of thyroid hormones can mean that your metabolism is too high, which can mean that you lose weight quickly and can lose muscle mass if you don’t eat enough. This can then yo yo back to a slow metabolism and too much weight gain in the future.

So you can see that your thyroid hormones are very important for optimising your fertility, and your diet is essential for a healthy thyroid. If you’re trying to conceive, make sure that you get your thyroid hormones checked, then see a dietitian to discuss:

  • How much iodine you should be taking,
  • Your intake of goitrogens,
  • When to take your nutritional supplements,
  • Whether or not you need any vitamin D supplements, and
  • Optimising your metabolism.

In the meantime, download my fertility diet meal plan here.

And, as always, if you have any questions, or experiences you’d like to share, id love to hear about them in the comments boxes below.



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