Fertility seems like it should focus solely on the reproductive system, but it can be impacted by our other bodily systems and functions. For example, the endocrine system, a complex network of glands and organs, is responsible for releasing hormones into the circulatory system (aka the bloodstream). These hormones control and coordinate your body's metabolism, energy level, reproduction, growth and development, and response to injury, stress, and mood. 

The thyroid is a part of that messenger system of glands within the endocrine system, and when your thyroid is not functioning correctly, it can have a profound impact on your overall health and fertility. Now let’s dive into what exactly the thyroid does and how it can affect reproduction. 

What does the thyroid do?

The thyroid is a butterfly-shaped gland located in your neck, just above your collarbone. Despite its size, the thyroid plays a pivotal role in the endocrine system. From how fast your heart beats to how quickly your body burns calories, your thyroid directly influences things as subtle as your mood and as vital as your fertility. 

So, how does it work? The thyroid gland receives signals from the pituitary gland in the brain, which sends out a hormone called thyroid-stimulating hormone (TSH). TSH tells the thyroid gland how much triiodothyronine (T3) and thyroxine (T4) to produce and secrete. If your thyroid is functioning normally, it produces the exact amount of hormones needed to keep your body’s metabolism running and in balance so that it can transform the food you eat into the energy you need. 


When the thyroid doesn’t create and release enough thyroid hormone into your bloodstream, this is called hypothyroidism. Also known as underactive thyroid, hypothyroidism slows down your metabolism and can make you feel tired, gain weight, and be unable to tolerate cold temperatures. 

Hypothyroidism can also cause: 

  • Thinning hair
  • Constipation
  • Irregular periods
  • Loss of sex drive
  • Pale skin
  • Infertility
  • Miscarriage
  • Premature Birth


Hyperthyroidism is the exact opposite. An overactive thyroid occurs when your thyroid gland produces too much of the hormone thyroxine (T4). Hyperthyroidism can accelerate your body's metabolism, causing adverse reactions such as a rapid or irregular heartbeat.  

Hyperthyroidism can also cause:

  • Weight loss
  • Increased appetite
  • Nervousness or anxiety
  • Disrupted sleep
  • Fewer or lighter menstrual cycles
  • Increased sweating
  • Heat intolerance 

Thyroid health and fertility: What's the connection?

Both hypothyroidism and hyperthyroidism can have a negative impact on fertility and increase the risk of miscarriage and premature birth, so you’ll want to make sure to get your thyroid levels checked prior to starting to try to get pregnant. 

With hypothyroidism specifically, low levels of thyroid hormone can interfere with the release of an egg from your ovary, also known as ovulation. In addition, some of the underlying causes of hypothyroidism — such as Hashimoto’s Thyroiditis — can negatively impact fertility due to the presence of autoimmune antibodies. 

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Hyperthyroidism, on the other hand, can cause accelerated weight loss, which may result in fewer or lighter menstrual cycles. This, obviously, has a negative effect on your fertility. Without a regular or healthy menstrual cycle, your chances of conception lower significantly. 

Can thyroid issues be treated?

Yes. The good news is that after consulting with your doctor, most cases of hypothyroidism can be successfully treated with oral medication. Typically taken once a day, this can help regulate thyroid function. Your doctor will want to have your blood checked about 4–6 weeks after starting the medication to confirm that you are taking the right dose and see if any adjustments are needed. There are also several treatment options for hyperthyroidism, depending on the cause.

Being in tune with your whole body, not just your reproductive system, and advocating for yourself can make all the difference when it comes to your fertility. If you are experiencing any of the above signs or symptoms, are generally feeling “off,” or if you simply want to make sure your thyroid is working correctly, there is a simple way to find out for sure. 

Labcorp OnDemand’s Thyroid Stimulating Hormone Blood Test measures a hormone that stimulates the thyroid to produce T3 and T4, two hormones that play a critical role in controlling the body’s metabolism. After easily purchasing it with a credit card or using your HSA/FSA, you can visit a convenient Labcorp patient service center for blood collection. Results are delivered to you in just a couple of days. Click here to learn more!

Kristyn Hodgdon is the Co-Founder and Chief Creative Officer at Rescripted.