Why You Need To Look At Thyroid Health For Optimal Fertility

Why You Need To Look At Thyroid Health For Optimal Fertility

This guest blog post was written by naturopathic physician, Dr. Kalea Wattles, ND.

Disclaimer: the information in this article is for educational purposes only and is not designed to replace individualized recommendations from a practitioner. Always check with your doctor before adding supplements or making changes to your treatment plan.

When women decide they want to get pregnant, one of the first questions I ask is: “how’s your thyroid doing?” Adequate thyroid function is extremely important in terms of fertility (and pregnancy)— this little gland has a very big job!

The Basic Players in Thyroid Health

The thyroid is a butterfly-shaped gland in the front of the neck and is responsible for regulating growth and metabolism.

This important task requires constant communication with the brain.

Thyroid stimulating hormone (TSH) comes from the pituitary gland in the brain, which is sometimes called the "master gland" of the body. TSH triggers the thyroid to release two major hormones: T4 (thyroxine) and T3 (triiodothyronine).

Most of the hormone circulating in the blood is T4, a less potent form of thyroid hormone. The body then converts T4 to T3, which is the less abundant, but more potent.

These thyroid hormones travel through the bloodstream to nearly every cell, helping your body utilize energy and grow or repair tissue.

How Can Thyroid Levels Impact Fertility?

Thyroid hormones affect the reproductive tract, including the inside of the ovary.

That’s right— thyroid hormones can bind to the surface of ovaries and to the actual egg cells inside them, influencing their growth and development.

Either too little thyroid hormone (hypothyroidism) or too much thyroid hormone (hyperthyroidism) can have an effect on fertility.


Let’s start with hypothyroidism, because this is the more common scenario.

Women with an under-active thyroid tend to experience dry skin, constipation, weight gain, hair loss, fatigue, and sensitivity to cold temperatures. And those who use basal body temperature for fertility tracking probably see a chronically low temp.

I often hear a theme of feeling sluggish and heavy— both physically and emotionally. Even periods tend to be heavy and irregular!

Here are some additional ways an under-active thyroid can affect fertility:

Can Cause Hormonal Imbalances

Hypothyroidism can cause problems with the way the body makes, uses, and detoxes hormones like estrogen and testosterone.

The resulting hormonal imbalances can cause delayed puberty, menstrual cycle irregularities, and subfertility.  

Can Prevent Ovulation

Low thyroid function can lead to “anovulatory” cycles (no ovulation), meaning hormones weren’t able to do their job maturing an egg inside the ovary and signaling that it should be released.

Can Increase Prolactin

Hypothyroidism can cause elevated levels of prolactin, a hormone that comes from the brain and is normally elevated in breastfeeding women.

Prolactin can also interfere with the hormones that are responsible for stimulating the ovaries to develop and release an egg every month.

Remember that thyroid function is important for men’s fertility too. Low thyroid function can affect both the sperm volume and sperm motility (their ability to swim forward in a semi-straight line), as well as decreasing libido.


Less common, but still very important: hyperthyroidism.

Women with too much thyroid hormone can feel anxiety, racing heart, loose bowel movements, weight loss, and sensitivity to warm temperatures. Menstrual cycles will likely become irregular and sex drive tends to decrease.

Here are some more ways an overactive thyroid can pose problems for fertility:

Can Cause Hormonal Imbalance

Hyperthyroidism makes it more difficult for your body to get rid of excess estrogen and testosterone.

This can cause hormone imbalances that affect ovulation, delay your period, and cause fertility challenges.  

Can Prevent Ovulation

Women with hyperthyroidism have consistently high levels of another hormone called “luteinizing hormone” (LH).

Normally LH peaks in the middle of the cycle, triggering an egg to be released.

When LH just hangs out at a high level instead of having a mid-cycle spike, no egg is released.

Should I Have My Thyroid Tested?

Roughly 4% of reproductive age women in the United States have diagnosable hypothyroidism, including around 1/3 of women experiencing subfertility.

This number probably increases to about 8% if we include women with “subclinical hypothyroidism,” meaning they don’t quite meet criteria for hypothyroidism, but their thyroid definitely isn’t functioning optimally.


Who is Eligible for Testing?

While current guidelines do not recommend universal thyroid screening for women who are trying to get pregnant, testing is generally recommended under the following conditions (which by my calculations, is almost everyone!):

      • Previous history of a thyroid disease.
      • Those who have had surgery or radiation treatments performed to the head or neck.
      • Personal history of any autoimmune disease or family history of autoimmune thyroid disease.
      • Over the age of 30.
      • History of early labor, pregnancy loss, or infertility (meaning no pregnancy after one year of trying with perfectly timed intercourse).
      • Body mass index (BMI) over 40.
      • Living in areas of known iodine deficiency (iodine is required for thyroid hormone synthesis).


What Tests Should be Done?

Thyroid function can be assessed with a simple blood test.

A comprehensive thyroid panel likely includes:


The signal from the brain to the thyroid gland that hormone is needed. The higher the TSH, the louder the brain is screaming at the thyroid gland like, “Hello!!! We’re waiting for some hormone out here!”

TSH will be elevated in hypothyroidism and very low in hyperthyroidism.

Free T4

The more abundant, less potent hormone.

Free T3

The less abundant, more potent hormone.

Thyroid Antibodies

Autoimmune thyroid disease, which occurs when the body makes antibodies against the thyroid gland or its receptors on cells, is the leading cause of hypothyroidism in reproductive aged women.

Elevated antibodies are associated with increased risk of pregnancy loss, even if thyroid hormones are in a healthy range.

What If My Tests Come Back Abnormal?

There are medications to address both hypo and hyperthyroidism.

If your thyroid is under-active, your doctor can prescribe a thyroid hormone medication (there are a few different options to choose from). If you’re making too much hormone, there are also medications to lower your levels.

But the road doesn’t stop there. A functional approach to thyroid health means we need to look at all the determinants of your health.

Stress, chronic infection, toxic exposures, medications, nutrient deficiencies, and dietary habits can interfere with the amount of active hormone available to the body.


Top Diet & Lifestyle Modifications For Thyroid Health:

1. Focus On Thyroid Support Nutrients

Zinc and selenium are super important to both produce thyroid hormone and to convert T4 into T3.

Nutritional Sources of Zinc: Oysters, Pumpkin Seeds, Crab, and Beef.

Nutritional Sources of Selenium: Brazil Nuts, Tuna, and Turkey.

2. Employ Stress Management Techniques

This is a big one! Chronic stress can affect thyroid hormone synthesis and decrease the conversion of T4 to T3, leaving your cells hungry for thyroid hormone.

If you don’t have a tried and true stress reduction method, now is the perfect time to explore!

Techniques To Consider: Mindfulness Based Meditation, Deep Breathing Exercises, Yoga/Moderate Exercise, Journaling.

This is also where I love to bring an acupuncturist and some botanical medicine on board.

3. Address Inflammation

The body perceives inflammation as a stressor, which we already know leads to sub-optimal thyroid health. Think about underlying sources of inflammation like chronic infection, food sensitivities, or toxic exposures.

I highly recommend keeping regular wellness exams with your doctor and don’t forget about the dentist! Gum disease is a surprising source of chronic inflammation for many people.

4. Check Your Meds

Many medications can interfere with thyroid function, but a common one I see in reproductive age women is the birth control pill.

The high doses of estrogen in oral birth control can cause the liver to produce a protein called “thyroxine binding globulin" (TBG). TBG binds free thyroid hormone in the blood and makes it unavailable to cells, essentially inactivating it.

Oral birth control also depletes many of the important nutrients we talked about for thyroid hormone production, including zinc and selenium.

If you’ve been taking oral birth control you might need a little nutrient boost and some extra care to your thyroid to get your hormones in good working order.

Have I Convinced You To Pay Attention To Your Thyroid Health?

Thyroid health is so important for optimal fertility! We’ve got to show our thyroid some love if we want to have a healthy hormone balance, regular periods, optimal fertility, and abundant energy to live our best lives.


Dr. Kalea Wattles (ND) is a Naturopathic Physician specializing in women’s health, fertility, and Functional Medicine. She is a firm believer that women deserve to have it all: family, career, and abundant good health. She holds dear the philosophy that fertility isn’t all about making babies and that women with knowledge of their fertility status are empowered to make informed decisions about growing babies, businesses, or whatever it is they are hoping to bring into this world!

Kalea serves as a Clinical Coordinator at the Institute for Functional Medicine where she develops curriculum for advanced training in male and female hormones, thyroid and adrenal function, and gut health. She is currently building her new medical practice, Functional Fertility, offering fertility-focused telemedicine. In her spare time, she enjoys exploring the Pacific Northwest with her husband and two daughters.


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