TSH and Fertility: Everything You Need to Know

Thyroid-stimulating hormone (TSH) plays an important role in your overall health and metabolism – so it’s no surprise that it plays a role in your reproductive health too!

TSH works by triggering the thyroid gland (a part of the endocrine system) to produce the right amount of thyroid hormones. These hormones then go on to help regulate the growth and function of several bodily systems, including the reproductive system.  

In terms of reproductive health, research shows that thyroid hormones influence things like ovulation, egg to fetal development, and miscarriage prevention. However, they must be in balance to keep things functioning properly. 

In this article, we’ll cover everything you need to know about the connection between TSH and fertility, including the impact of thyroid dysfunction on reproductive health and how to manage optimal levels.

Key Takeaways

• TSH (thyroid-stimulating hormone) helps to stimulate the production of thyroid hormones T4 (thyroxine) and T3 (triiodothyronine). 
• Both T4 and T3 play an essential role in regulating the menstrual cycle and fertility
• When thyroid hormones are out of balance, this can lead to a number of fertility challenges including anovulation, irregular ovulation, polycystic ovaries, shortened luteal phase, hyperprolactinemia, and early onset perimenopause/menopause.
• Among individuals with thyroid autoimmunity, research shows an increased prevalence of infertility and pregnancy loss

Understanding TSH and Its Role in Fertility

What is TSH?

TSH (Thyroid Stimulating Hormone) is a type of hormone produced by the pituitary gland (a small structure found at the base of the brain). Its primary function is to control the thyroid gland (often referred to as just the “thyroid”) in order to help stimulate the production of the thyroid hormones known as T4 (thyroxine) and T3 (triiodothyronine). 

According to the Society for Endocrinology, both T4 and T3 are essential for multiple bodily functions including metabolism, digestion, heart function, muscle control, brain development, and bone activity. They also play a key role in regulating the menstrual cycle. 

TSH levels and fertility 

When thyroid hormones are too high (or too low), the pituitary gland responds accordingly by reducing (or increasing) TSH. This imbalance of hormones can then have an impact on the menstrual cycle and fertility. 

Some of the most common fertility challenges related to an imbalance of thyroid hormones include anovulation, irregular ovulation, polycystic ovaries, shortened luteal phase, hyperprolactinemia, and early onset perimenopause/menopause.

Why test for TSH?

If you have been experiencing irregular menstrual cycles and/or struggling to get pregnant, it may be worth getting your TSH levels tested. A TSH test can be used to assess thyroid functioning, diagnose thyroid disorders, and determine whether or not your thyroid is interfering with your reproductive health. 

How can TSH levels be tested?

TSH levels can be tested with a simple blood test at your doctor’s office. 

Alternatively, you can also test for TSH from the comfort of your home with an at-home test kit – such as Mira’s own Panorama Lab Test. In addition to TSH, Mira’s Panorama Lab Test can also screen for thyroxine (fT4), anti-mullerian hormone (AMH), prolactin, and free testosterone. 

Testing for these five hormones at once can provide key insights into your overall fertility, ovarian reserve, thyroid functioning, and more. 

The Impact of Thyroid Dysfunction on Fertility

Hyperthyroidism

When TSH levels are abnormally low, this may indicate that the thyroid is overactive and producing too much thyroid hormone. This is called hyperthyroidism, and it can cause symptoms such as:

• Weight loss
• Irregular heartbeat
• Irritability and mood swings
• Tiredness, weakness, and fatigue
• Difficulty sleeping
• Enlarged thyroid gland

One of the most common causes of hyperthyroidism is an autoimmune disorder known as Graves’ disease. This disease, if left untreated, can disrupt the menstrual cycle and lead to irregular periods. This in turn may impact an individual’s ability to get pregnant. 

Common treatments for hyperthyroidism include medications (such as thioamides and/or beta-blockers), radiotherapy, and in rare cases surgery. 

 

Hypothyroidism and Fertility

When TSH levels are abnormally high, this may indicate that the thyroid is underactive and not producing enough thyroid hormone. This is called hypothyroidism, and it can cause symptoms such as:

• Weight gain
• Depression
• Tiredness
• Muscle aches

When it comes to fertility, low levels of thyroid hormone can interfere with the body’s ability to ovulate – making it very difficult to conceive. Research also suggests that women with higher than average TSH levels may also have lower egg quality and quantity compared to women with normal TSH levels, which can also have a negative impact on fertility. 

Additionally, low thyroid hormone levels are also associated with a shortened luteal phase (sometimes referred to as luteal phase deficiency). When the luteal phase is too short, it can be difficult for a fertilized egg to successfully implant itself in the uterine lining. This is due in part to progesterone levels not being elevated enough to facilitate the implantation process. 

If you think that your progesterone levels may be too low due to a shortened luteal phase, it may be worth tracking your hormones on a more regular basis. This can be done at home with the Mira App and Monitor, which can measure PdG (pregnanediol glucuronide, the urine metabolite of progesterone) levels in urine. 

Common treatments for hypothyroidism include taking iodine supplements and thyroid hormone therapy – which may help to reduce the risk of miscarriage in individuals with hypothyroidism and/or autoimmune thyroid disease. 

TSH Levels, ART, and IVF Outcomes 

Assisted Reproductive Technologies (ART)

We know that having thyroid issues carries an increased risk of infertility, often resulting in the need for some help with assisted reproductive technologies (ART). Alongside treatment with ART, thyroid hormone therapy can also help to improve the chances of conception and carrying a pregnancy to term.  

However, research is just beginning to dive further into the role that thyroid hormone therapy can play in fertility treatments. For instance, research from the American Thyroid Association suggests that thyroid hormone therapy doesn’t improve pregnancy rates, live birth rates, or preterm birth rates in women using ART to get pregnant. However, it may improve miscarriage rates (relative to women who did not receive thyroid hormone therapy). 

Much more research is needed in this area in order to fully determine the impact of thyroid dysfunction on fertility.  

In vitro fertilization (IVF)

TSH levels are considered one of the key measures of fertility and how an individual may respond to IVF treatment. They are not an absolute indicator, but we do know that thyroid dysfunction is linked with adverse pregnancy outcomes. 

So what does the research say? Controversy about TSH thresholds before ART remains, and some studies suggest that cut-off levels are too low which may lead to overdiagnosis and unnecessary treatments. However, a retrospective study found better outcomes of live births when patients undergoing IVF had a certain serum TSH level (≤3 mIU/L) before treatment.  

More research in the area is needed and optimal TSH levels before assisted reproductive technologies remain controversial.  

Thyroid Autoimmunity and Its Effects on Fertility

In some cases, the body produces antibodies that mistakenly attack the thyroid. This is known as thyroid autoimmunity, and it is a frequent cause of thyroid dysfunction prevalent among women of reproductive age.   

Because of its potential impact on fertility and pregnancy, this condition has drawn much attention from researchers trying to understand the connection between thyroid autoimmunity and fertility. 

Thyroid autoimmunity and infertility

Several studies have found an increased prevalence of thyroid autoimmunity in those with infertility, and some have even found correlations with other conditions like polycystic ovary syndrome (PCOS) and endometriosis. Research is ongoing and study limitations have impacted results. It is clear though that there is an association between thyroid autoimmunity and decreased fertility. 

More research is needed so we can have a better understanding of the physiological underpinnings of thyroid autoimmunity and how it can be treated in order to improve fertility outcomes.  

Thyroid autoimmunity and pregnancy

When it comes to pregnancy, there is a well-documented increased risk of pregnancy loss among individuals with thyroid autoimmunity. In a large, retrospective study, researchers found that there was an independent association between thyroid autoimmunity and adverse pregnancy outcomes. This verifies the increased risks of pregnancy-related complications and outcomes in pregnant women with positive thyroid autoantibodies. 

If you are planning a pregnancy, this is an important factor to discuss and monitor with your healthcare team, especially if you are already concerned about your thyroid function. 

Managing TSH Levels for Optimal Fertility

Check-in with your doctor

If you are actively trying to plan a pregnancy, it’s a good idea to have your doctor check your thyroid levels with a blood test. This is especially true if you have had thyroid issues at some point in your past. Your doctor will be able to then provide the very best guidance based on your individual situation, medical history, and fertility goals. 

Consider your broader hormone health and lifestyle

So much about our everyday life can impact our hormone health – and this includes the functioning of our thyroid. Here are just a few different lifestyle tips that can help to keep your hormones balanced naturally. 

Make sure to get plenty of sleep

Sleep plays a critical role in our body’s ability to regulate its hormones and manage basic bodily functions. Doctors typically recommend that adults get between 7-9 hours of sleep each night. 

Watch your stress levels

Chronic stress can also lead to long-term hormone imbalance. Yoga, meditation, exercise, and setting aside plenty of time each week to do something you enjoy are all great strategies for keeping stress levels in check. 

Maintain a healthy, nutrient-rich diet

The foods that we eat can also have a profound impact on our hormones. Diets that are high in protein, fiber, and healthy fats help to fuel the body and regulate blood sugar. They also help us maintain a healthy weight. 

Seek help when you need it

Planning a pregnancy can feel overwhelming and even isolating at times. If you have concerns about any symptoms or lifestyle changes, or maybe you’re just struggling to cope emotionally, it’s important to reach out to someone you trust! Whether it’s your friends, family members, or a support group, there are people out there ready to listen and help. 

Mira’s own fertility coaches can provide expert guidance in the areas of fertility planning, wellness, nutrition, hormone health, and more! 

Conclusion: The Significance of Understanding TSH for Fertility

Thyroid hormone levels are critical for your reproductive health, and when they are too high or too low, it can make the path to parenthood that much more challenging. Suboptimal levels may cause issues with menstruation, egg quality, and ovulation. And during pregnancy, low levels could impact fetal development. 

If you are looking to plan a pregnancy now or in the future, monitoring your thyroid health is especially important. Testing is easy, and early treatment can lead to more successful outcomes. If you have concerns about your thyroid function, or other risk factors like a family history of autoimmune disease, speak to your healthcare provider for treatment options and monitoring. Individual factors like age, history, and lifestyle choices can all factor into TSH levels and fertility, and personalized advice is always best.  

FAQs

Can thyroid disorders affect male fertility as well?

Yes. Research shows that thyroid dysfunction in male individuals may lead to semen abnormalities including reduced semen volume, reduced sperm density, reduced sperm motility, and reduced sperm morphology. 

How do I know if I have a thyroid problem?

Some of the most common symptoms of thyroid dysfunction include:

• Weight fluctuations
• Irritability, mood swings, and depression
• Tiredness and fatigue
• Temperature sensitivity (i.e. frequently feeling too hot or too cold)
• Difficulty sleeping

The only way to diagnose a thyroid problem is by having your TSH (thyroid stimulating hormone) levels tested by your doctor. 

How long does it take to resolve thyroid issues?

Thyroid issues can take up to a few weeks and even a few months to resolve. The time it takes will depend on the type of thyroid disorder and individual treatment plan. 

What should I do if I have infertility due to thyroid issues?

If your fertility has been compromised due to thyroid issues, the first step is working with your doctor to get your thyroid under control. An endocrinologist (a doctor who specializes in glands and hormones) or even a reproductive endocrinologist can work with you to manage your hormones. 

Can subclinical hypothyroidism affect fertility?

Although the general opinion is that subclinical hypothyroidism (a mild form of hypothyroidism) may increase difficulties with fertility and pregnancy, the research consensus is less clear.  

There is disagreement over TSH level limits, and preliminary research suggests that treatment for subclinical hypothyroidism may improve pregnancy outcomes – but not necessarily fertility.  More research is needed in the area, but if you suspect that subclinical hypothyroidism is affecting your fertility, it’s worth a conversation with your doctor about your treatment options.