When you’re trying to conceive, it can sometimes feel like there’s an overwhelm of information and advice, tests, and emotions. Amidst all the information, one factor that often gets overlooked is thyroid health. If you’ve been told that your thyroid levels are “normal” based on standard tests, it can be easy to brush off any concerns. However, your thyroid health plays a much bigger role in fertility than you might think. Even small imbalances in thyroid function—whether it’s an underactive or overactive thyroid—can have a significant impact on your ability to conceive. By taking a deeper look at your thyroid function and supporting it through targeted nutrition, lifestyle choices, and comprehensive testing, you can optimise your thyroid health to greatly improve your chances of conceiving.

Understanding the Thyroid Gland

The thyroid is a small, butterfly-shaped gland in your neck, but it plays a central role in regulating many of your body’s key functions. This little powerhouse produces two primary hormones—T4 (thyroxine) and T3 (triiodothyronine)—that influence everything from metabolism and energy production to your reproductive health. When the thyroid is functioning well, these hormones help maintain balance in your body, ensuring that everything from ovulation to menstrual cycles is working as it should. But even slight imbalances in thyroid hormones can disrupt this balance, leading to issues that may make it harder to conceive.

The Link Between Thyroid Health and Fertility

Thyroid dysfunction, whether it’s hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), can disrupt the delicate hormonal balance needed for fertility. Here’s how even subtle thyroid imbalances can impact your ability to conceive:

1. Ovulation Disruptions

Thyroid hormones influence key reproductive hormones like oestrogen, progesterone, and luteinising hormone (LH), which are essential for regular ovulation. Therefore, when the thyroid isn’t functioning correctly, it can lead to disrupted ovulation. For example, in hypothyroidism, lower levels of LH may prevent ovulation altogether, making it difficult to get pregnant. If you’re not ovulating, there’s no egg to fertilise, and conception can’t occur.

2. Menstrual Irregularities

Thyroid problems can also result in irregular or even absent periods. Women with hypothyroidism might experience long, irregular cycles, or in more severe cases, may stop menstruating altogether. In contrast, hyperthyroidism can cause periods to become lighter and shorter. Since having regular periods is key to tracking ovulation and timing intercourse, these disruptions can make it harder to predict your fertile window, reducing your chances of conception.

3. Poor Egg Quality

Egg quality is another crucial factor when trying to conceive, and thyroid health can influence this too. Both hypothyroidism and hyperthyroidism can impact how eggs develop in the ovaries, potentially leading to poorer egg quality. Since thyroid hormones play a role in regulating follicle-stimulating hormone (FSH)—which is responsible for egg maturation—an imbalance can impair the development of healthy eggs, making it harder to achieve a pregnancy.

4. Miscarriage Risk

An untreated thyroid disorder can increase the risk of miscarriage. Thyroid hormones are critical during the early stages of pregnancy when fetal development is at its most sensitive and hypothyroidism in early pregnancy has been linked to an increased risk of miscarriage. Maintaining optimal thyroid function can help reduce this risk and support a healthy pregnancy.

5. Impact on Male Fertility

Thyroid health is just as important for men when it comes to fertility. Hypothyroidism in men can lead to low testosterone levels, low sperm count, and reduced sperm motility—problems that make it more challenging for sperm to fertilise the egg. So, it’s important that both partners consider their thyroid health when trying to conceive.

The Thyroid and Fertility Test Results: What You Need to Know

Many women are told that their thyroid function is “normal” based on a simple TSH (thyroid-stimulating hormone) test. However, this may not always tell the full story, especially if you’re still experiencing symptoms of thyroid dysfunction, like fatigue, weight gain, or difficulty getting pregnant.

1. TSH Levels: A Basic Overview

TSH is often the first test doctors use to measure thyroid function. This hormone is produced by the pituitary gland and signals your thyroid to produce T4 and T3. Typically, a TSH level between 0.4 and 4.0 mIU/L is considered normal, but from a functional medicine perspective the optimal range for fertility should be between 1.0 and 2.0 mIU/L. If your TSH is higher than this, you may still be dealing with thyroid dysfunction, even if the test doesn’t show an obvious problem.

Some women also experience subclinical hypothyroidism, where their TSH is elevated but T4 and T3 levels remain normal. This can still impact fertility, as the body may not be functioning optimally at a cellular level.

2. T3 and T4 Levels

While TSH is a helpful starting point, it doesn’t give a full picture of your thyroid health. To get a more complete understanding, understanding your T3 and T4 levels is crucial. While T4 is produced in greater quantities by the thyroid, T3 is the active form of the hormone that your cell use. It’s possible for someone to have normal TSH levels but still experience thyroid dysfunction if their body isn’t converting T4 into T3 effectively.

3. Thyroid Antibodies

Thyroid antibodies are a crucial factor to consider when evaluating thyroid health, particularly if you suspect an autoimmune condition. High levels of thyroid antibodies, such as anti-TPO (thyroid peroxidase) antibodies, may point to autoimmune thyroid disorders like Hashimoto’s thyroiditis or Graves’ disease. These conditions can lead to fertility problems and may often go undiagnosed without specific testing.

4. Free T3 and Free T4 Tests

In addition to total T3 and T4 levels, it’s also important to check the “free” versions of these hormones—Free T3 and Free T4. These are the active forms of thyroid hormones that are readily available for use in your body. Low levels of Free T3 and Free T4 can indicate thyroid dysfunction, even if your total thyroid hormone levels appear to be normal.

Thyroid health is key to fertility, and even if your thyroid tests appear “normal,” subtle imbalances could still be affecting your reproductive health. By adopting a holistic approach—through proper nutrition, stress management, and comprehensive testing—you can optimise thyroid function and improve your chances of conception. If you’re struggling with fertility, seeking a healthcare provider who takes a thorough, integrated approach to both thyroid health and reproduction can make all the difference.

Ready to take the next step in supporting your fertility? Join the waitlist for my upcoming fertility programme. Together, we’ll dive deeper into understanding your thyroid and other factors affecting your fertility, helping you feel empowered and confident on your journey to conception. Join the waitlist today!