Facing Infertility with Normal Thyroid Function? This May Be Why!

Trying to conceive can be an incredibly stressful experience for all parties involved. It is frustrating to face repeated disappointment when your strongest desires are to have an uneventful pregnancy and a healthy baby. When there are additional physical health conditions involved, trying to conceive becomes even more emotionally taxing. We know that this is frequently the case for women with hypothyroidism. Unfortunately, however, many people don’t know that this is also frequently the case for women who appear to have normal thyroid function. Many women whose doctors have told them time and time again that their thyroids are functioning well and that their thyroid function shouldn’t affect their ability to get pregnant are still faced with difficulty conceiving, repeated miscarriages, other negative pregnancy outcomes, and failed fertility treatments such as in-vitro fertilization.

The Evasive Norm that is TSH

You may know that thyroid stimulating hormone (TSH) is the most commonly run lab test to evaluate thyroid function. What you probably don’t know, though, is the fact that the “normal” value for TSH has been hotly debated over the years. On January 18th, 2001, the American Association of Clinical Endocrinologists (AACE) issued a press statement that said that “Even though a TSH level between 3.0 and 5.0 uIU/ml is in the normal range, it should be considered suspect since it may signal a case of evolving thyroid underactivity.” In spite of this statement, physicians still disagree on what constitutes a “normal” TSH and at what value it becomes appropriate to treat a thyroid disorder.

This may be because the data from some pretty important studies suggest that the “ideal” or reference range for TSH isn’t as reliable as we once thought. The authors of a National Health and Nutrition Examination Survey III (NHANES III)-based study looked at the relationships between TSH and two types of thyroid antibodies in pregnant women. At the end of this study, researchers concluded that when we initially looked at thyroid function and came up with the “normal” values for the TSH reference range, we may have been wrong about the upper limit because of certain confounding factors.

I discussed the thyroid antibodies that these researchers looked at in a previous article on why TSH is not the entire story as far as evaluating thyroid function is concerned. In order to comprehensively evaluate thyroid function and take a more comprehensive look at your hormone status, we need to look at a full thyroid panel including other thyroid labs. As we’ll see, the results of these other labs can dramatically affect fertility, even when TSH is “normal”.

Why the TSH Debate is Problematic for Women with “Normal” Thyroid Function Who Are Trying to Conceive

Researchers wanted to find out if having a TSH value that fell within the brackets of “normal” but was on the higher side (of normal) experienced a difference in outcome for fertility treatments compared to those with optimal thyroid function. Here’s what they found: women who had a TSH above 2.5 mIU/L got pregnant at a rate of 21.6%, while women with TSH values at 2.49 mIU/L and below conceived at a rate of 56.6%—more than double that of their counterparts on the higher end of normal. Keep in mind that the normal value for TSH is typically 0.45 mIU/L to 4.50 mIU/L plus or minus 0.5mIU/L. This indicates that, according to this reference range, women with a TSH of 2.5 mIU/L are basically in the average or midline bracket.

Thyroid Antibodies in Women with “Normal” and Unknown Thyroid Function

In addition to having a TSH in the upper half of the normal range, having positive thyroid antibodies can negatively impact fertility. Researchers looked at 11 different studies with women undergoing in-vitro fertilization who tested positive for thyroid antibodies. What they found was that having positive antibodies increased their risk of miscarriage. In another study, women undergoing intrauterine insemination (IUI) didn’t seem to have these problems, which is great! That study did have quite a few limitations, though, so there is reason for caution.

A third study looked at women with positive thyroid antibodies and those with negative thyroid antibodies. They further divided the women into those who they were sure had subclinical hypothyroidism (e.g. increased TSH with normal T4 thyroid hormone), those who they were sure didn’t (e.g. normal TSH and T4), and those whose statuses were unknown (e.g. not sure about their TSH and/or T4 values). This study found that, of the women with unknown subclinical hypothyroidism statuses, both those who tested positive for thyroid antibodies and those who tested negative were able to conceive at roughly the same rate, but there was an increased risk of miscarriage and decreased likelihood of delivery in women with positive thyroid antibodies compared to women with negative thyroid antibodies.[/vc_column_text]

The same study further found that among those who definitely did not have subclinical hypothyroidism, clinical pregnancy rate, miscarriage rate, and delivery rate were all similar, regardless of whether they had positive antibodies or not. This indicates that the presence of thyroid antibodies in and of itself doesn’t lead to worse pregnancy outcomes. In other words, just because you do have thyroid antibodies doesn’t necessarily mean you’ll be at increased risk for negative pregnancy outcomes. Instead, the increased risk for negative outcomes occurs when the thyroid autoimmunity is allowed to progress to the point that the TSH begins to rise. That’s when we begin to see the negative pregnancy outcomes such as miscarriages, and so on.

Now that we know the problem, the solution should be simple, right? Address the antibodies before the autoimmunity has the opportunity to progress and enjoy the positive impact on fertility! Researchers tried to do that, and here’s what happened.

A Simple Fix? Maybe Not…

Before we proceed, I want to make sure you’re tracking with me. To summarize, we have a situation here where the progression of events is as follows: thyroid antibodies lead to an increased TSH value, which then leads to increased risk for miscarriages and other negative pregnancy outcomes.

Now here’s what happened:

In an attempt to address this problem, researchers conducted a clinical trial that included 600 women with normal thyroid function and positive thyroid antibodies who were undergoing IVF and embryo transfer. They divided the women into two groups and gave one group synthetic thyroid hormone in an attempt to reduce negative outcomes associated with positive antibodies. At the end of the study, researchers found that these women who had TSH values within the “normal” range and tested positive for thyroid antibodies did not have better outcomes than woman with similar lab results who were not given levothyroxine. In other words, the levothyroxine did not help reduce the rate of miscarriage or increase the rate of live births.

So the Levothyroxine Didn’t Help… Now What?

Researchers’ and patients alike were undoubtedly disappointed by the results of this study. The next step in the quest to decrease thyroid autoimmunity’s effects on fertility was to go back to the drawing board and try to find a therapy that would address thyroid autoimmunity in order to improve pregnancy outcomes. Fortunately for us, however, there has already been lots of research done on ways (and natural, non-invasive ways at that!) to decrease thyroid antibodies.

As an example, scientists found that supplementing myoinositol and selenium significantly reduced the risk of developing hypothyroidism in individuals with normal thyroid function and positive thyroid antibodies. At the end of on study, researchers found that those who had TSH levels on the higher end of the reference range prior to undergoing treatment saw a reduction in their TSH values. Lab work at the end of the study showed that the therapy actually modulated the immune system in a way that decreased inflammation and the levels of thyroid antibodies also declined. This suggests that myoinositol and selenium actually helped prevent the progression of autoimmunity which could have potentially led to a subclinical hypothyroid state and, eventually, a state of overt hypothyroidism.

Factors That Influence Thyroid Function, Autoimmunity, and Fertility

In addition to micronutrients like myoinositol and selenium, there are a variety of other factors that can influence thyroid function, autoimmunity, and fertility as a whole, whether you choose to try to conceive naturally or undergo fertility treatment to help with conception.

These factors include:

  • Overall macronutrient and micronutrient status
  • Blood sugar control
  • Environmental burden or toxic load
  • Reproductive hormone balancing
  • Other forms of autoimmunity that may negatively impact fertility
  • Genetic concerns that may lead to negative fertility outcomes
  • And more

If you have been struggling with fertility and would like professional help in preparing your body for pregnancy and setting yourself up to minimize potential complications, click here to learn more about working with us.