The Thyroid Fertility Connection


It’s time to take a deeper look at the health of your thyroid.

We check full thyroid panels regularly in our practice for patients who are trying to conceive and in those that become pregnant. Why? More than 12 percent of the U.S. population will develop a thyroid condition during their lifetime. An estimated 20 million Americans have some form of thyroid disease, and up to 60 percent of those with thyroid disease are unaware of their condition. Furthermore, thyroid hormone affects the ability to conceive, as well as, outcomes of both mom and baby. This article will help you understand hypothyroid and hyperthyroid conditions and symptoms, thyroid hormone and it’s relationship to conception and pregnancy, optimal thyroid hormone ranges for those trying to conceive, and issues with our current model of testing.

If you're wondering whether your symptoms indicate an early-stage thyroid condition or if suboptimal thyroid could be affecting your ability to conceive or hold on to a successful pregnancy, feel free to contact us with any questions!

Hypothyroidism and Hyperthyroidism

What's the difference? Hypo means "less" and indicates an underactive thyroid. This means your thyroid is not producing enough of its key hormones. This is more common in women than men and is more common among those over 60 years old. 

Hyper means "overactive", and means your thyroid is overreacting to the body's signals and overproducing the hormone thyroxine. This speeds your metabolism and creates a number of problems. It is associated with Graves’ disease (discussed below). 

Thyroid Health and its Connection to Fertility

Irregular Cycles and Interference with Ovulation:

Thyroid abnormalities are one of the leading causes of menstrual irregularities. The endocrine system is one large symphony of hormones with each hormone constantly interacting with other hormones in a series of negative feedback loops. HYPOthyroidism causes a decrease in FSH and LH, two hormones released from the pituitary gland that signal egg maturation and release (aka ovulation). Additionally, low FSH and LH further disrupts hormone balance because these hormones are necessary for the production of estrogen and progesterone from ovary.

Abnormal Sperm

In men, elevations in thyroid hormone impairs sperm motility, while low thyroid can cause abnormal sperm morphology and lead to erectile dysfunction.

Increased risk of Miscarriage:

Both hypothyroid and autoimmune thyroiditis increases the risk of miscarriage. Research shows that TSH above 2.5mIU/L presents an increased risk of miscarriage in early pregnancy. Furthermore, thyroid antibodies, even in patients with normal thyroid levels, increase the risk of miscarriage. Thyroid antibodies can be elevated without elevated TSH; therefore, it is not only important to test your thyroid levels, but also your antibody levels. 

Poor Maternal Outcomes:

High levels of free T4 have been associated with increased risk of preeclampsia, a serious condition characterized my high blood pressure and protein in the urine, usually accompanied by swelling in the hands and feet. This risk is especially pronounced if the woman also has low hCG during her pregnancy. Furthermore, women with preeclampsia during their pregnancy have an increased risk of developing hypothyroidism later in their life. Additionally, hypothyroidism during pregnancy increases risk of other maternal complications, such as, postpartum bleeding and postpartum depression.

Poor Fetal Outcomes:

Hypothyroidism, even in the subclinical form, is associated with intrauterine growth restriction and lower APGAR scores. Furthermore, hypothyroidism in pregnancy increases the risk of premature delivery, congenital anomalies, and fetal retardation.

10 Symptoms of Hypothyroidism 

  1. Constipation 

  2. Persistent Fatigue 

  3. Hair Loss 

  4. Muscle and Joint Aches and Pains  

  5. Variable Periods

  6. Unexplainable Weight Gain

  7. Low Appetite 

  8. Hoarse Voice

  9. Brain Fog and Trouble Concentrating 

  10. Sensitivity to Cold 

10 Symptoms of Hyperthyroidism:  

  1. Anxiety and restlessness 

  2. Racing Heart 

  3. Insomnia 

  4. Unexplainable Weight Loss

  5. Ravenous Appetite  

  6. Excessive Sweating 

  7. Multiple Bowel Movements 

  8. Thin, Brittle Hair

  9. Bulging or puffy eyes 

  10. Hand tremors 

Why Thyroid Testing Often Fails: 

Using TSH as the Sole Marker of Thyroid Function

In conventional medicine, it is considered standard of care to run a screening thyroid stimulating hormone (TSH) test before ordering any other thyroid lab tests. TSH is a hormone released by the pituitary gland that signals the thyroid to make more thyroid hormone. If everything is working properly, the body balances TSH levels with an inherent negative feedback mechanism to decrease TSH when circulating thyroid hormone is high, and to increase TSH when circulating thyroid hormone is low. But there are three major issues with relying on TSH as the SOLE parameter: 

Problem 1: Misleading Reference Range

The range for "normal" TSH of 0.5-5.0 is misleading and is the main reason for the epidemic of under-diagnosed thyroid conditions. Many individuals will find themselves right in the middle of that range around 3, yet feeling miserable and left with no answer as to why. Not only do these broad reference ranges leave many people in misery, but they also allow thyroid disorders to silently progress until they become "bad enough" to treat! For this reason, many thyroid specialists have developed their own functional ranges to detect a system that isn't functioning optimally in order to initiate supportive measurements to hopefully alleviate symptoms and stop the progression to a more serious thyroid condition. 

When it comes to fertility, this becomes even more of an issue, as a TSH above 2.5 has been associated with an increased risk of miscarriage and other pregnancy complications.

Problem 2: TSH is an Indirect Marker

TSH should reflect the level of actual circulating thyroid hormone, but in some cases, our internal feedback mechanisms can be a little off! This happens most often when the issue is arising at the level of the hypothalamus or pituitary, where thyroid releasing hormone (TRH) and TSH are produced, respectively. There are a number of reasons for hypothalamic and pituitary dysfunction, including, but not limited to: a traumatic brain injury, severe blood loss during childbirth, past or present eating disorders, PTSD, and even significant chronic stress!

Problem 3: Partial and Incomplete Picture 

Running TSH only gives us ONE piece of a very complex puzzle. Thyroid issues can arise from a number of areas. It is not only important to get a full thyroid picture for proper detection, but it is also crucial for proper treatment! Thyroid replacement is not the only treatment that should be initiated with a thyroid condition, and it is important to know where the pathway went awry, so further work can go into detecting and addressing the root cause. 

What Other Lab Tests Should Be Considered? 

Thyroid Hormone Levels: 

When looking at the thyroid function, it only makes sense to look at levels of T4 and T3, your two thyroid hormones circulating in the bloodstream. Furthermore, it is essential that free T4 (fT4) and free T3 (fT3) be assessed, as the free form of the hormone is unbound from a protein and actually able to bind to the receptor site to initiate the appropriate response. When thyroid hormones are bound by protein, they are not free to act. Therefore, some individuals may be experiencing thyroid symptoms despite having adequate levels of T4 and T3 if their level of the binding protein is high. 

Reverse T3 Levels: 

Of the total amount of thyroid hormone produced by the thyroid, roughly 80% is T4 and 20% is T3. Later down the line, much of T4 is converted into T3, which is much more potent than T4. Some of T4 is converted into reverse T3 (rT3), an inactive form of T3.  Not only does this take away from the production of active T3 hormone, but rT3 also inhibits the function of T3, as it competes for binding sites at the receptor. Some level of rT3 is normal and healthy to prevent hyperthyroid symptoms, but under certain conditions, the body produces too much rT3, which results in hypothyroid symptoms. Conditions that increase production of rT3 include: 

  • Acute illness or injury 

  • Increased stress and adrenal issues 

  • Low caloric diet and low carbohydrate diets

  • Chronic disease and chronic inflammation 

Antibodies: Hashimoto’s and Grave’s Disease: 

Hashimoto's thyroiditis, an autoimmune attack on the thyroid, is the number one reason for hypothyroidism is the United States, yet many individuals walk around without knowingly suffering. In the beginning stages of Hashimoto's, thyroid levels may come back normal or even high on labs, this is because the thyroid will spit and spatter hormones as it is under this initial attack. Eventually, as the thyroid further breaks down and loses function, the individual will often settle into chronically low thyroid levels. This is yet another reason why TSH may be "normal," yet a serious thyroid condition goes undetected.  When treating Hashimoto's thyroiditis, it is important to not only replace thyroid hormone, but it is also essential to identify what is fueling the autoimmune condition and put a stop to further destruction. In some cases, the trigger can be as simple as gluten in the diet! The main two antibodies tested in Hashimoto's thyroiditis are thyroperoxidase antibody (TPOAb) and thyroglobulin antibody (TGAb). 

Graves’ disease is Hashimoto's counterpart and the number one cause of hyperthyroidism. Graves' disease is also an autoimmune disorder, although this one is rarer. In some cases, Graves' disease is left untreated until it progresses to the point where the individual needs to have the thyroid gland surgically removed, leading to permanent hypothyroidism. The key to treating Graves' is early detection, and this is done by checking for thyroid stimulating antibodies (TSIAb) 

Optimal Thyroid Levels 

In the world of functional medicine, we not only want you to be "diagnosis free," we also want you to feel your best! That is why we look to achieve OPTIMAL thyroid levels with complete symptom resolution. These can change slightly depending on the individual and the lab; however, the following is roughly where I find people feeling their best! 

  • TSH: 0.5-2.0 IU/mL

  • F43: 15-23 pmol/L

  • fT3: 5-7 pmol/L

  • rT3: < 10:1 ratio for rT3:fT3

  • TPOAb, TgAB < 4 IU/m

Three Important Takeaways: 

  1. "Normal" is not always normal

  2. Don't question, get tested!

  3. Truly treating a thyroid disorder goes way beyond simply giving a thyroid replacement hormone. 

Next Steps

If you'd like to discuss your symptoms or testing options, our doctors offer a free 15-minute initial consultation. We can discuss your health concerns and allow you to determine whether you'd like to move forward with testing or treatment