How Thyroid Function Influences Fertility

The little butterfly shaped organ that sits at the base of your neck is a big deal for health and fertility. I like to think of the thyroid as a thermostat for the body, influencing temperature, hormone balance and metabolism.

When thyroid imbalance is left unmanaged it can lead to a variety of symptoms including premature ovarian failure, unexplained infertility or an ovulation disorder like Polycystic Ovarian Syndrome.

The thyroid impacts the menstrual cycle in many ways due to the cascade of hormones that is involved in successful ovulation. Our thyroid hormone is part of this cascade and is supposed to support the hormone communication that occurs between our brain and our ovaries. This communication coordinates when an egg matures and when it is released (ovulation). When the thyroid isn’t functioning properly, these lines of communication are disrupted and can show up in a variety of ways.

One of the many reasons to track your cycle includes the fact that early signs of thyroid imbalance can be caught:

• If you are tracking your cycle with basal body temperature (BBT) you can pinpoint an underactive thyroid when BBT consistently falls below 97.5 degrees F during the preovulatory or follicular phase.

• A cycle consistently longer than 35 days

• Cycles shorter than 21 days

• Very heavy period flow or bleeding for more than 7 days

• Abnormal patterns of cervical mucus

• Postovulatory phase (luteal phase) of 10 or less days

Thyroid imbalance is very common, with women being 5-10 times more likely than men to have a thyroid disorder. Research shows that even mild thyroid conditions increase the risk of miscarriage. 

Even when thyroid function (measured with TSH) looks “normal”, it is important to look at symptoms and consider a full thyroid panel including thyroid antibodies. Thyroid antibodies significantly increase risk of miscarriage even if all other thyroid hormones are normal. When thyroid antibodies are present it means the immune system is attacking your thyroid leading to inflammation and tissue damage. This is known as Hashimoto’s Thyroiditis, the most common thyroid disorder in the USA. 

Looking at Thyroid Stimulating Hormone (TSH) and free Thyroxine (FT4) is standard in conventional medicine. However, looking at TSH and T4 alone don’t tell us the full story. A FULL thyroid panel is recommended for appropriate assessment of thyroid function.

Its really important to get your thyroid checked out if you have a history of miscarriage, PCOS, unexplained infertility, or premature ovarian failure. A full thyroid panel includes:

• TSH

• Free T4

• Free T3

• Reverse T3

• Thyroid peroxidase antibodies (Anti-TPOAb)

• Thyroglobulin antibodies (Anti- TgAb)

A standard “normal” range for TSH is 0.45-4.5 IU/L. However, as soon as you are pregnant the range changes to 0.45-2.5 IU/L. A growing body of research shows that the optimal range for TSH is 0.45-2.0 IU/L, which is the range I recommend for my clients during preconception.

You might be wondering what leads to thyroid imbalance. There isn’t any one thing, rather it’s typically a combination of factors that contribute to thyroid dysfunction. Here are the major factors that impact thyroid function:

• Poor gut health. The bacterial balance in the gut can increase inflammation, decrease ability to digest nutrients and trigger an autoimmune response.

• Nutrient deficiencies as a result of poor gut health or eating a diet lacking in nutrients that the thyroid needs to function like iodine, selenium, zinc, iron, and B vitamins.

• High exposure to toxins like fluoride, chloride, bromide, pollutants, pesticides, xenoestrogens and more. Our detox system relies heavily on nutrients to be able to eliminate these toxins from the body, so the first two factors also influence toxic burden on the body.

• Being on hormonal birth control long-term or more than 2 years consecutively

• Chronic stress

• Poor sleep quality

As you can see the factors contributing to thyroid imbalance are complex and can be very challenging to navigate on your own. I recommend starting with improving stress management, sleep quality and adding nutrient dense foods to your diet. 

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