Thyroid, Fertility, and Pregnancy: An Integrative Functional Approach

Thyroid disease is common in women of reproductive age, and plays an important role in fertility problems, pregnancy complications, and postpartum ailments.

In this article we’ll address hypothyroidism and Hashimoto’s Disease, so let’s get clear on the definitions before we dive in. Overt hypothyroidism is generally diagnosed when a person has a high TSH and a low free T4. Subclinical hypothyroidism, on the other hand, represents mild thyroid failure when TSH is high, but free T4 is in the normal range (though different definitions of subclinical hypothyroidism have been used in different studies). Hashimoto’s Disease is the number one cause of hypothyroidism in the U.S., and is caused by an autoimmune disease.¹

Just how common is thyroid disease? Per the American Academy for Clinical Chemistry, overt thyroid disease affects approximately 5% of American women of reproductive age.² The American Thyroid Association (ATA) estimates that up to 1% of pregnancies are impacted by full blown hypothyroidism, and subclinical hypothyroidism (a more mild form) affects up to 15% of pregnancies (and these are just the thyroid conditions they know about).³,⁴

If that seems insane, that’s because it is!

But, what’s even more insane is that the vast majority of women are not routinely screened as part of their annual checkups, preconception counseling, or even maternal checkups.

How can this be when thyroid conditions are so common before, during, and after pregnancy?

While there is little controversy about the importance of treating overt hypothyroidism in reproductive health, subclinical hypothyroidism is a whole different ball game.

And it’s important to understand this is not your doctor or midwife’s fault… the problem lies in a lack of understanding about the symptoms and risk factors for thyroid disease coupled with insufficient evidence surrounding subclinical hypothyroidism and conflicting recommendations about who needs to be screened and when.

And that’s what this article is all about…so buckle your seatbelts and get ready to take back control of your maternal health.

How thyroid disease impacts women and their babies

Before we get into all the specifics on screenings, symptoms, autoimmunity, labs, etc. it’s important you understand how thyroid disease impacts your fertility, reproductive health, and even the health of your unborn baby.

Your thyroid, a butterfly-shaped gland that sits at the base of your neck, produces thyroid hormones which are responsible for and/or play a role in a variety of bodily functions like metabolism, regulating your gut viscera (which is involved with motility, digestion, production of enzymes, etc.), sleep, cholesterol, ovulation, and menstruation…to name a few.

Given its role in regulating ovulation and menstruation you can see why thyroid problems can cause fertility problems. Hypothyroidism has not only been implicated in anovulation (failure to ovulate), it has also been shown to influence progesterone production, estrogen metabolism, circulating levels of sex hormone‐binding globulin, granulosa cells (which surround and supply nutrients to developing oocytes in the ovary), as well as the oocytes themselves.⁵

Insofar as pregnancy is concerned, maternal hypothyroidism is a risk factor for:⁶,⁷, ⁸

• miscarriage/early pregnancy loss
• placental abruption
• gestational hypertension
• preeclampsia
• anemia
• postpartum hemorrhage

Neonatal complications of hypothyroidism in pregnancy include preterm birth, low birth weight, developmental delays, congenital malformations and death.⁹,¹⁰, ¹¹ It’s important to note that baby’s brain development in early pregnancy is dependent on mom’s T4—a type of thyroid hormone we’ll discuss more coming up.¹²

This isn’t meant to scare you, but to highlight the importance of proper thyroid management during preconception and pregnancy. So keep reading, because it’s definitely possible to conceive and have a healthy pregnancy with hypothyroidism—but it’s best to be informed, because you might have to advocate for yourself.

As an additional catch-22, pregnancy actually increases your risk for thyroid disease, which is why many women wind up with mysterious symptoms of fatigue, hair loss, weight gain, depression, anxiety, etc. postpartum and down the line.

Pregnancy also increases the risk for autoimmune diseases including Hashimoto’s. We know that the risk of autoimmune disease is much higher in the first year after vaginal delivery,¹³ and according to one study “44.3% of women who develop an autoimmune disease have onset after the first year of pregnancy.”¹⁴ So if you didn’t have Hashimoto’s before pregnancy, you might want to test again after—especially if you are struggling with postpartum health issues.

As you can see, the thyroid is absolutely essential to a healthy and successful pregnancy, birth, and motherhood…

…which brings us back to: why on earth aren’t more women being screened and properly treated for thyroid disease prior to getting pregnant, when pregnant, and beyond? Let’s look at that now.

Why aren’t women being screened for thyroid disease/TSH?

The short-answer is two-fold: #1: a lack of understanding and awareness about the risk factors for thyroid disease, and #2: ever-changing recommendations from medical associations related to insufficient evidence surrounding subclinical hypothyroidism.

The guidelines are there, in writing, they’re just not black and white (unfortunately).

Let’s start off by reviewing the screening recommendations from different associations.

As of 2015 The US Preventive Services Task Force (USPSTF) recommends against routine screening for thyroid disease among nonpregnant adults.¹⁵ Which doesn’t bode well for proactive individuals looking to identify thyroid disease before getting pregnant…which is ideal.

The American College of Obstetrics and Gynecology (ACOG) also recommends against universally screening women for thyroid disease.¹⁶

To top it off, the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA) also recommend against universal screening for patients who are pregnant or planning pregnancy.

However, according to the 2012 AACE Clinical Practice Guidelines For Hypothyroidism in Adults “aggressive case finding” should be considered for patients who are planning pregnancy.¹⁷

And the 2017 ATA Guidelines for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum recommend testing TSH for all women seeking care for infertility.¹⁸

So who should be screened? While there is no consensus about screening the population for hypothyroidism, “aggressive case finding” is appropriate for women with any of the following risk factors:¹⁹,²⁰

• Clinical signs and/or symptoms of thyroid disease—like fatigue, hair loss, cold sensitivity, weight gain, depression, irregular periods, dry skin, muscle aches etc.
• Presence of goiter or abnormal thyroid on physical exam
• Personal history of thyroid issues
• First-degree relative with autoimmune thyroid disease
• History of preterm birth, miscarriage, and/or infertility
• Multiple prior pregnancies
• Over age 30
• Thyroid antibodies like Thyroid Peroxidase (TPO) and/or Thyroglobulin (TG) antibodies (which providers rarely check for!)
• Type 1 diabetes or presence of other autoimmune disorders
• High body mass index
• Previous head or neck radiation, including dental x rays without a neck shield which was routine prior to 1970²¹
• Living in an iodine deficient region
• Psychiatric disorders like anxiety, depression, postpartum depression etc
• Use of the medications amiodarone or lithium
• Adrenal insufficiency
• Anemia or pernicious anemia
• High cholesterol or hypertension
• Vitiligo

I don’t know about you, but that sums up the vast majority of women I know who are trying to conceive (either as their doctor, or as their friend)…implying that we should be screening most women.

And in a 2015 review published in the The Obstetrician & Gynaecologist (TOG), researchers agreed that abnormalities in thyroid function can have an adverse effect on fertility and reproductive health, while increasing the chance of miscarriage and adverse pregnancy and neonatal outcomes. They acknowledge that “with appropriate screening and prompt management, these risks can be significantly reduced.”²²

2014 guidelines from the European Thyroid Association (ETA) “informally” concur with ATA and ACOG regarding universal screening: “…however, these guidelines note that while not formally recommended, most of the authors support universal screening given that a substantial number of women with thyroid dysfunction may be missed with targeted screening strategies.”²³, ²⁴

So I am not the only one advocating that we check our patients for a very common issue… it’s just not an official recommendation.

Can thyroid problems affect fertility?

Given the somewhat conflicting recommendations we just read through you may be wondering if thyroid problems truly affect fertility.

I can say with confidence there is a connection between thyroid and fertility.

Most fertility experts know about the thyroid-fertility connection, but wouldn’t you rather know the facts before you wind up at a fertility specialist?! I know I would, so let’s look at the research and recommendations.

In one study examining data on infertile women between 2000 and 2012, women with a diagnosis of unexplained infertility were found to have TSH levels on the higher end of normal than the control population (TSH > 2.5 mIU/L).²⁵ What this means: even mild variations of thyroid dysfunction within the normal range can result in difficulty conceiving. (All the more reason to check in with your levels and get ahead of any issues.)

In another study of almost 400 women with infertility, 24% were found to have hypothyroidism (63% subclinical and 37% overt). After treatment with levothyroxine (LT4), 76% of women were able to conceive within 6 weeks to one year. The authors conclude that measurement of TSH should be done early in infertility check ups, and “simple, oral hypothyroidism treatment for 3 months to 1 year can be of great benefit to conceive in otherwise asymptomatic infertile women.”²⁶

In a retrospective study titled Thyroxine Treatment May Be Useful For Subclinical Hypothyroidism In Patients With Female Infertility, it was reported that 84% of infertile women with subclinical hypothyroidism (TSH > 3.0 mU/L) not only successfully conceived but conceived faster while taking LT4 therapy.²⁷

Another study conducted on patients with subclinical hypothyroidism undergoing in-vitro fertilization (IVF), found those who were being treated with LT4 for their condition improved embryo quality and pregnancy outcomes vs. those who were not treated.²⁸

While some studies have found increased rates of infertility among women with subclinical hypothyroidism, other studies have not. For example, a retrospective study found higher rates of subclinical hypothyroidism (13.9% vs. 3.9%) in infertile women as compared to fertile controls. ²⁹ However a prospective study showed no increased rates of subclinical hypothyroidism among infertile women (but researchers in this study did report slightly higher TSH levels (1.3 vs. 1.1 mU/L) in the infertile women compared to controls).³⁰

The research on subclinical hypothyroidism and fertility speaks volumes, however there are no controlled trials demonstrating that treatment with LT4 in women with subclinical hypothyroidism (not undergoing IVF) increases the likelihood of conception. Thus, the official recommendations cite “insufficient evidence” which is why there’s not a stronger general consensus.

So what are the official recommendations?

The 2012 AACE guidelines recommend treatment with thyroid medication (LT4 or levothyroxine) for women of childbearing age with the following lab parameters:³¹

• TSH > 2.5 mIU/L during preconception
• TSH > 2.5 mIU/L in the first trimester of pregnancy
• TSH > 3.0 mIU/L in the second trimester
• TSH > 3.5 mIU/L in the third trimester

According to the 2017 ATA guidelines “despite imperfect data, the majority of evidence appears to support an association between overt thyroid dysfunction and an increased risk of infertility. Thyroid dysfunction is also reversible, and treatment is generally safe and may exert a positive effect on fertility. Therefore, it is reasonable to treat overt thyroid dysfunction in infertile women, with the goal of normalizing thyroid function.”³²

However, given the lack of controlled trials, the 2017 ATA Guidelines state that there is insufficient evidence to determine if treatment with medication improves fertility for subclinical hypothyroidism. Yet they recognize that treating subclinical hypothyroidism may be considered given its ability to prevent the progression to hypothyroidism once pregnancy is achieved, and the minimal risk.³³

I’m all about risk vs benefit, and in this situation there are low risks and potentially profound  benefits with a very simple, widely available and inexpensive intervention.

Hashimoto’s Disease and Fertility

Hashimoto’s Disease is an autoimmune disease characterized by Thyroid Peroxidase (TPO) and/or Thyroglobulin (TG) antibodies to the thyroid. It is associated with a higher risk of fertility issues including miscarriage and preterm birth.³⁴

The good news is some research has proven those risks go down if the condition is diagnosed and properly treated with thyroid medication (I should know, because I have Hashimoto’s and had 3 healthy babies, but I do believe that this condition contributed to recurrent pregnancy loss before I was diagnosed).

Let’s take a look at the research on Hashimoto’s and fertility…

A 1994 prospective study of 87 euthyroid women who were positive for TPO and/or TG antibodies, found 20% of women in the study developed a serum TSH > 4 mU/L during gestation despite normal TSH levels preconception. This finding supports the claim that in women with autoimmune thyroid disease and normal thyroid function, hypothyroidism can occur in pregnancy and per the authors “justifies systematic screening of thyroid autoimmunity during pregnancy.”³⁵

In a prospective, randomized interventional trial, Negro and colleagues studied euthyroid (which means “normal thyroid function”) women with TPO antibodies. Researchers showed that in women with thyroid autoimmunity, hypothyroidism can occur because of the stress of pregnancy, thus increasing the risk of miscarriage and premature deliveries. They showed that treatment with LT4 can help lower these risks.³⁶

In another retrospective study, data was analyzed from 65 pregnant women with TPO antibodies and a normal TSH value at the first prenatal visit. 34 of these women were treated with 50 mcg LT4 daily, while the others were not treated. The results: all of the 34 LT4-treated women had successful pregnancies, but 5 of 31 untreated women (16%) experienced miscarriage. Based on their results, authors favor universal screening and treatment with levothyroxine for autoimmune thyroid disease during pregnancy.³⁷ Per the ATA: “although limited in nature, these data support the findings of Negro et al and begin to suggest a potential benefit to this treatment approach.”³⁸

That said, other research has shown no benefit. For example, a study by the United Kingdom National Institute for Health Research showed no benefit of treatment in women with normal TSH and thyroid antibodies.³⁹ However, in that study everyone’s TSH went up to 3.5 mIU/L and everyone was treated with the same 50 mcg dose of medication (vs. weight based dosing or specific dosing based on labs)…which, to me, shows some significant limitations in the study.

And in a study titled: Effect of Levothyroxine on Miscarriage Among Women With Normal Thyroid Function and Thyroid Autoimmunity Undergoing In Vitro Fertilization and Embryo Transfer, women were treated with 25-50 mcg of LT4 and no difference was found in pregnancies and live births.⁴⁰ However, though the researchers determined these women had “normal” thyroid function, their TSH ranges were up to 4.78 mIU/L (which is higher than the 2.5 mIU/L recommended by AACE) and dosage was not determined by weight (which is most effective).

Despite some conflicting evidence, benefits seem to outweighs risk and the 2012 AACE Clinical Practice Guidelines for women who are pregnant or planning a pregnancy, including assisted reproduction in the immediate future, are as follows:⁴¹

• Treatment with LT4 should be considered in women of childbearing age with normal serum TSH levels if they have or have had positive levels of serum TPO antibodies, particularly when there is a history of miscarriage or past history of hypothyroidism. (Recommendation 19.2)
• Women should be treated with LT4 if their TSH is greater than 2.5 mIU/L and they have or have had positive levels of serum TPO antibodies. (Recommendation 19.3)
• Women with positive levels of serum TPO antibodies or with a TSH greater than 2.5 mIU/L who are not being treated with LT4 should be monitored every 4 weeks in the first 20 weeks of pregnancy for the development of hypothyroidism. (Recommendation 19.4)

That part I just shared about previous history of antibodies is powerful (so write it down!) because hardly anyone is told about it or tested for it when they’re planning to get pregnant or become pregnant.

The 2017 ATA Guidelines for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum are similar but less conclusive:⁴²

• Although there is limited data, treatment with LT4 may be considered in euthyroid (normal thyroid function) patients with positive thyroid antibodies, especially for women with a history of miscarriage given its potential benefits in comparison with its minimal risk.
• Women with Hashimoto’s disease should have their TSH measured at the time of pregnancy confirmation and every 4 weeks through mid-pregnancy since hypothyroidism may occur because of the stress of pregnancy.

Bottom line: proper treatment and close monitoring of TSH is essential if you either have Hashimoto’s or have ever had thyroid antibodies.⁴³

So please, if you’ve ever tested positive for Hashimoto’s/thyroid antibodies work closely with your doctor or Midwife. And if you’ve never been tested for thyroid antibodies, now might be the time!

From my perspective as a physician and functional medicine expert, since there is clear and ample scientific evidence that Hashimoto’s negatively affects fertility and pregnancy outcomes (as outlined above) and that treatment with medication is low-risk, I’d opt in favor of treatment for most of my patients hands-down. As always – talk to your doctor about your unique needs.

Do fertility treatments affect thyroid medication?

They can for sure…but not always.

Remember, your thyroid is intimately connected with your reproductive system and other hormones, thus any changes in other hormone levels can impact how your medication works.

The research is a bit inconclusive, but per the ATA some studies have shown that the estrogen increases during in-vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (ICSI) could affect TSH, and free thyroid hormone.⁴⁴

For example, during and up to one month after ovarian stimulation serum TSH was increased in three of five studies while free T4 increased in two studies, decreased in one, and remained unchanged in another.

Another study found TSH levels increased in women during and directly after IVF but returned to normal when pregnancy was achieved.

The ATA also cites research suggesting that increasing thyroid medication during IVF is beneficial. Because of this, the ATA recommends the following: “When possible, thyroid function testing should be performed either before or 1–2 weeks after controlled ovarian hyperstimulation because results obtained during the course of controlled ovarian stimulation may be difficult to interpret.”⁴⁵

They also recommend TSH increases be treated in women who get pregnant following controlled ovarian hyperstimulation (a fertility treatment used to induce ovulation by multiple ovarian follicles). For women who do not become pregnant following treatment but experience mild TSH elevations, they recommend re-checking serum levels after 2-4 weeks.

To be on the safe side I say: test don’t guess!

To sum it up (who actually needs to be treated before pregnancy)…

To sum it all up…when trying to conceive, who should actually be considered for treatment with thyroid hormone? Official guidelines support treatment if you meet any of the following criteria:⁴⁶

• TSH > 2.5 mIU/L
• TSH > 2.5 mIU/L if you have or have ever had positive levels of TPO antibodies
• Normal TSH if you have or have ever had positive levels of TPO antibodies, particularly if there is a history of miscarriage or past history of hypothyroidism.
• After IVF if TSH increases and pregnancy is achieved

Note that the upper limit of the normal reference range for TSH (outside of pregnancy) is around 4.5-5 mIU/L depending on the lab you use. So your labs will not be flagged as abnormal, and if you are trying to conceive or pregnant this is an important distinction. And your healthcare provider may or may not know this given all the conflicting info flying around…so take note and discuss with them!

And remember: thyroid labs should be measured as soon as you have a positive pregnancy test, and every 4 weeks through mid-pregnancy if you have Hashimoto’s and/or hypothyroidism. If undergoing IVF, TSH should be measured either before or 1–2 weeks after controlled ovarian hyperstimulation and again after 2-4 weeks if pregnancy is not achieved.

Scrutinizing screening: why the TSH test isn’t enough

By now I’ve (hopefully) convinced you that it’s in your best interest to advocate for testing (ideally) before getting pregnant.

But—and this is key—I would argue that you need more than just the standard Thyroid Stimulating Hormone (TSH) test to evaluate for thyroid dysfunction.

There are a number of reasons for this, and best summarized in the Journal of Thyroid Research:

“While this approach (measuring TSH only) has been successful in many ways, it has some grave limitations. This includes the basic question of what constitutes an agreed reference range and the fact that the population-based reference range by far exceeds the variation of the intraindividual set point. Both problems result in a potential misdiagnosis of normal and pathological thyroid function in a substantial proportion of patients.”⁴⁷

Be aware that this is even more controversial than what I’ve outlined above about subclinical hypothyroidism, so this may not be your doctor’s practice. However, I fall back on risk vs. benefits and clinical experience on this one.

To get a full picture of a patient’s thyroid health and manage thyroid medication, I find some of the following labs to be clinically very helpful in managing and titrating medication:

• TSH
• Total T4 and T3 if pregnant
• Free T4 and T3 outside of pregnancy
• Thyroid Peroxidase (TPO) and Thyroglobulin (TG) antibodies

In pregnancy, specifically, a total T4 is recommended over free T4. This is because pregnancy increases serum binding proteins and free T4 may yield lower values based on reference ranges established with nonpregnant people.⁴⁸ Likewise I would check a total T3 in pregnancy over a free T3.

And I wholeheartedly believe that addressing the root cause of autoimmunity will help lower thyroid antibodies over time. I see this every day in my clinical practice.

I discuss this more in A Functional Medicine Approach to Hashimoto’s Thyroiditis and Hypothyroidism.

Can I have a healthy pregnancy with hypothyroidism?

Yes you can! But, you need to do three things:

#1: Get your thyroid treated properly before getting pregnant. Remember: TSH should not be above 2.5 mIU/L.

#2: Work with your doctor closely to properly manage and likely increase your medication dose by 30% as soon as you get that positive pregnancy test.⁴⁹ More on this below.

#3: Monitor your labs closely and frequently, which typically means every 4 weeks if pregnant and/or taking fertility drugs.

Your treatment options will vary based on your lab work, history, and if you have antibodies (Hashimoto’s) or not. So, you’ll want to talk to your doctor and/or midwife OR you can work with me on the Hashimoto’s and hypothyroidism piece (though I can’t replace your very important fertility or prenatal team) if you’re in Colorado, Texas, or Michigan.

I cannot stress the importance of treatment enough as hypothyroidism during pregnancy has been associated with many adverse outcomes, including: up to a 60% increased risk of pregnancy loss, in addition to increasing your risk for hypertension, premature birth, low birth weight, fetal death, impaired cognitive development, and lower IQ in baby.⁵⁰ So yeah, it’s important!!

Now, the medication management piece is incredibly important…and not enough people know about it, so let’s review.

Do I need to increase my thyroid medication when pregnant?

Yes you probably do!

This is due to shifts in hormones like estrogen and increased demands for thyroid hormone. How do you increase medication and when? You’ll need to work with your doctor and/or midwife on this, so let’s look at specifics.

Per the ATA, between 50-85% of women on LT4 need to increase their medication during pregnancy. However, how much to increase depends on the etiology of your condition (Hashimotos, existing functional thyroid tissue, etc.) and your levels pre-pregnancy.⁵¹

They go on to recommend the following for women with normal thyroid hormone levels receiving once-daily dosing of LT4 (regardless of the dosage): “an increase by two additional tablets weekly (nine tablets per week instead of seven tablets per week, giving a 29% increase) can effectively mimic gestational physiology and thus prevent maternal hypothyroidism during the first trimester. Another option is to increase the dosage of daily LT4 by approximately 25%–30%.”

Additionally, as of 2017 the ATA “strongly recommends” based on “high quality evidence” that hypothyroid patients on LT4 should independently increase their dose of LT4 by 20-30% (which equals 2 additional tablets weekly) and notify their caregiver promptly for testing and further evaluation.

This means, per the ATA, that you can safely increase your medication levels on your own, once you get that positive pregnancy test so long as you get in for screening and evaluation ASAP. Wow, I wish more people knew about this—so pass it on! And be sure to discuss this with your doctor or midwife so you are all on the same page.

This is consistent with what I recommend in my practice as I’ve found most women need an increased dose of 30% as soon as they get a positive pregnancy test. And we monitor their levels very closely by re-checking serum levels 4 weeks later.

Why so much monitoring?

Because TSH levels fluctuate during pregnancy, most notably decreasing during the first trimester, after which they rise for the second and third trimesters.⁵² Note, the downshift in TSH may be greater if you’re pregnant with twins or triplets than a single child.

Thyroid and fertility: Putting it all together

I’m so glad you found this article and took the time to read through the entire thing…because it’s so important to have the facts so you can advocate for yourself effectively.

The bottom line is this: your thyroid health can truly make or break your efforts to get pregnant, have a healthy pregnancy, and give birth to a healthy baby. The science is sound on that. Thus, it is in the best interest of every woman (I believe) to get screened before getting pregnant and discuss treatment options with their doctor if TSH levels are elevated above 2.5 mIU/L (to be on the safe side) and/or you’ve ever had a history of thyroid antibodies / Hashimoto’s Disease.

Believe me, it’s better to do this early on than suffer the physical and emotional heartache of miscarriages, an infertility diagnosis, and/or other pregnancy complications.

If you have reservations about being treated with medication, definitely share your concerns with your healthcare providers… but do keep in mind that risk benefit ratio!

In my opinion, the benefits of properly dosed thyroid medication during preconception and pregnancy far outweigh the risks. And I say this as a functional medicine physician who also believes that food is medicine, herbs are superhealers, and yoga just plain rocks.

Plus, there’s plenty you can do to naturally support your thyroid (as discussed in A Functional Medicine Approach to Hashimoto’s Thyroiditis and Hypothyroidism) as part of an integrative approach.

Speaking of an integrative approach, let’s work together on this!

Treating thyroid disorders in women in one of my areas of expertise…and I’d love to be of service to you.

I’m currently accepting a limited number of new patients in my functional medicine practice. When working with patients, I dive into a whole lot more than hormones… such as gut health, nutrient deficiencies, environmental exposures, and nutrigenomics. This includes extensive lab work, functional medicine testing, personalized supplement recommendations, a nutrition consult, and a truly custom treatment plan.

If you’d like to learn more (and are located in Colorado, Michigan, or Texas) click here to complete an application and we’ll be in touch.