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What You Should Know About High TSH Levels and Pregnancy

Written by Dr. Michael Ruscio, DC on September 27, 2022

Written by Dr. Michael Ruscio, DC on September 27, 2022 — Reviewed by Dr. Hannah Hamlin

How to Deal With Hypothyroid Issues When You’re Pregnant

• Some Thyroid Definitions|
• Thyroid Health During Pregnancy|
• Medication Benefits|
• High TSH While Trying to Conceive|
• Gut Imbalances and Hypothyroid Symptoms|
• Best Diet if You're Pregnant and Hypothyroid|
• Probiotics for Thyroid Problems|
• Important Nutrients|
• Pregnancy Hypothyroidism — A Special Case|

For most people with subclinical hypothyroidism (where the only lab value that’s out-of-range is thyroid-stimulating hormone or TSH), it’s often best to treat symptoms with diet and lifestyle changes and to avoid thyroid medications.

However, in the case of high TSH levels and pregnancy, it’s better to go straight for the medication route (taking thyroid hormone) to avoid complications with the pregnancy and baby. Getting your TSH levels checked regularly during pregnancy is essential for making sure you are producing (or taking) the appropriate amount of thyroid hormone.

Elevated TSH can make it harder to conceive, so women who have an underactive thyroid and are trying to get pregnant may also benefit from taking thyroid medication.

Keep in mind that if you do have elevated TSH levels, it’s absolutely possible to address the issue, to conceive, and to have a healthy pregnancy!

In this article, we’ll see what makes trying to conceive and being pregnant a special case when it comes to thyroid issues, and what you can do about it. We’ll also define the various types of thyroid imbalance and highlight some of the confusion around this topic. 

Some Common Thyroid Definitions

First let’s quickly understand some important definitions. When somebody has: 

Hypothyroidism…their thyroid gland is underactive. The patient will have high levels of TSH (thyroid-stimulating hormone) and low levels of free T4 (free thyroxine) hormone. Symptoms include fatigue, poor mood (feeling depressed), lack of concentration (brain fog), feeling cold, and difficulty losing weight 1 2.

Subclinical hypothyroidism… they have mildly elevated TSH levels but levels of free T4 that are still within the standard range. There may be mild symptoms of hypothyroidism 1.“A sluggish thyroid”…they may have been advised their levels of TSH and/or free T4 are “suboptimal” but within normal range. However, a sluggish thyroid is not an actual condition, and this diagnosis can distract from the fact that symptoms may be originating somewhere else, e.g, the gut.

If you are truly hypothyroid (known as overt or frank hypothyroidism) you will definitely benefit from thyroid hormone medication. But for a “sluggish thyroid” medication is absolutely not necessary.

In the case of subclinical hypothyroidism, medication may or may not be helpful depending on the circumstances. Being pregnant and trying for a baby are two of those circumstances where medication for subclinical hypothyroidism is good practice.

Your TSH Level is Key

Your TSH level is critical to planning out a medication strategy for pregnancy. It’s important to know that the acceptable range for TSH is different for pregnant and non-pregnant women.

According to the American Thyroid Association (ATA) and the American Association of Clinical Endocrinologists, TSH levels decline during the first trimester of pregnancy due to the rise in pregnancy hormones. TSH then rises again after 10-12 weeks of gestation 3. 

These fluctuations in hormone levels are why it’s so important to follow-up with your doctor and have your thyroid checked regularly during pregnancy — even if you have no history of a thyroid condition. 

In 2012, the ATA and American Association of Clinical Endocrinologists recommended that TSH levels should not exceed the following levels during pregnancy to avoid adverse pregnancy outcomes 3:

• First trimester – 2.0-2.5 mU/L
• Second trimester – 3.0 mU/L
• Third trimester – 3.5 mU/L

If your serum TSH levels stray outside these levels during pregnancy it is appropriate to take action with medication. Indeed pregnancy is a time when we should be meticulous with thyroid assessment so as to avoid TSH levels outside of the normal range.

Why Thyroid Health is Vital During Pregnancy

There’s more at stake when you have thyroid problems and are expecting a baby. Untreated high TSH levels and pregnancy can mean you run into pregnancy complications such as  3 4:

• An increased risk of miscarriage during the first half of pregnancy
• Placental abruption (a serious condition in which the placenta separates from the wall of the uterus before birth)
• Problems related to high blood pressure
• Stillbirth
• Impaired growth of the baby
• Abnormal nervous system and hormonal development in the baby

If very low thyroid hormone levels (normally associated with an elevated TSH) are not treated, it can cause difficulties in the baby’s brain development, which can impact IQ, movement, and language skills 5. 

Women who test positive for the presence of thyroid antibodies (a sign that the body’s immune system is attacking the thyroid gland) may also be more likely to experience fertility issues 6. Thyroid autoimmunity includes conditions like Hashimoto’s thyroiditis and Graves’ disease.

Because of the above, correcting any underactive thyroid issues with thyroid hormone replacement is critical for a woman who is pregnant or trying to conceive. This is likely to include women with subclinical hypothyroidism.

High TSH Levels and Pregnancy —  Benefits of Medication

The benefits of medication for pregnant women with subclinical hypothyroidism are more than just theoretical. For example: 

• A 2021 systematic review and meta-analysis looked at the health outcomes for pregnant women with subclinical hypothyroidism, some of whom were treated, and others who were not. It found that pregnant women who were treated had a lower risk factor for 7:
  • Pregnancy loss (miscarriage)
  • Premature birth
  • Pregnancy-related hypertension (high blood pressure). 
• A 2022 systematic review and meta-analysis also found that treating subclinical hypothyroidism with medication lowered the incidence of maternal hemorrhage and low birth weight 8.

Risks of Medication

It’s also important not to overtreat, however. In one study, women who were on thyroid hormone therapy the two years before conception had double the odds of having a preterm delivery, when their treatment was overzealous (TSH levels <0.10 mIU/L) 9.

A higher risk of preeclampsia and decreased birth weight have also been noted in women who have been overtreated with thyroid hormone 10.

Once again, this highlights how important it is to get TSH levels checked regularly in pregnancy to ensure that the mother isn’t under or overmedicated.

Which Medication is Best?

Everyone is different and you should talk with your healthcare provider to work out your own personal prescription for thyroid treatment during pregnancy.

However, the National Institute of Diabetes and Digestive and Kidney Diseases recommends that for hypothyroidism during pregnancy, levothyroxine, which directly increases T4 levels, is the best thyroid medication 11. Levothyroxine is safe for your baby and especially important for the baby’s brain development until he or she can make their own thyroid hormone.

Another popular hypothyroid medication, Armour Thyroid (made from animal thyroid), is not suitable for use while pregnant as it contains too much of the second type of thyroid hormone, T3. In the first trimester of pregnancy, T3 can’t cross into the baby’s brain like T4 can 11.

The use of T3 or desiccated thyroid hormone, like Armour Thyroid, can also decrease the amount of T4 available for the baby, potentially preventing normal development 3. For this reason, women who are taking desiccated thyroid hormone or T3 (Cytomel) should be switched to levothyroxine after becoming pregnant 3.

In short, during pregnancy, and likely also while trying for a baby, it’s important your hypothyroid medicine delivers only T4 hormone. You don’t need to worry about your baby getting T3, as any that your baby’s brain requires can be made from T4.

High TSH Levels While Trying to Conceive

Research suggests that TSH levels are also important when you’re trying for a baby. If you are struggling to get pregnant, it’s probably time to look into your thyroid health.

One study found that, out of 394 women with fertility issues, about 15% had subclinical hypothyroidism while another 8% had overt hypothyroidism 12. Notably, 76.6% of the women treated with thyroid hormone were able to get pregnant, suggesting that hypothyroidism was contributing to their fertility issues 12. Another study found that subclinical hypothyroidism was associated with a reduced clinical pregnancy rate 13.

On the other hand, women with TSH levels at the upper end of the normal range had similar fertility outcomes after undergoing assisted reproduction compared to women with lower TSH levels 14. This suggests that having a “sluggish thyroid” (TSH levels in the high-normal range) probably does not impair fertility.

Overall, more research is needed to better understand the level at which TSH is associated with negative fertility outcomes 10. In the meantime:

• Women trying to conceive should aim to keep within the non-pregnant reference range of thyroid function tests.
• Women who become pregnant should switch over and maintain within the pregnancy TSH range (see above).
• Women who have either subclinical hypothyroidism or overt hypothyroidism will likely benefit from thyroid medication in both cases (trying for a baby or being pregnant).

Gut Imbalance and Hypothyroid Symptoms

An unbalanced gut is an often overlooked factor in thyroid disease 15. Dysbiosis, which is when the microbes in your gut are out of balance is known to cause or be connected with 16:

• Inflammation, increased intestinal permeability (gut leakiness), and altered immune responses (both hypo and hyperthyroidism can result from autoimmune disease).
• Altered activity of enzymes that impact thyroid hormone levels.
• Reduced absorption of minerals that are important to the thyroid, including iodine, selenium, zinc, and iron. 
• Brain fog, depression, and other cognitive issues that overlap with thyroid symptoms 17 18.

Research also indicates that when gut problems are dealt with, thyroid health also improves, sometimes considerably.

For in-depth instruction on how to heal your thyroid naturally, you can now enroll in our online thyroid course. 

Best Diet if You’re Pregnant and Hypothyroid

Addressing poor gut health and food sensitivities through a good diet can make a big difference when it comes to your thyroid health. In fact, for most non-pregnant people, diet is the best way to tackle subclinical hypothyroidism.

At the Ruscio Clinic, we’ve found that following an elimination diet — in which you eliminate certain foods for a set period of time (usually 2-3 weeks) and then gradually reintroduce them while monitoring how you feel — is one of the best ways to improve hypothyroid symptoms for many people. 

However, pregnancy is not a time when you should eat a diet that is overly restrictive, so a good plan is to settle on eating a healthy whole-food diet with minimal processed and high-sugar foods instead.

A Paleo-style diet can be safe during pregnancy, but I wouldn’t recommend anything more strict. While the Paleo diet hasn’t been studied extensively for its effects on thyroid health, studies have shown that it can lead to improvements in fatigue, one of the most common and debilitating symptoms of thyroid disorders and pregnancy 19 20. 

One small study showed that a Paleolithic diet during pregnancy may have a beneficial effect on glucose tolerance and also increase iron stores and hemoglobin levels 21. 

Newborns of women maintaining a Paleolithic diet were slightly lighter but still a healthy weight, and there were no differences in health between the babies.

Probiotics for Thyroid Problems

Probiotics are supplements containing healthy gut bacteria that are safe to take during pregnancy and can help to improve both gut and thyroid function. For example:

• A meta-analysis of 10 randomized, controlled clinical trials concluded that probiotics can improve depressive symptoms (often associated with hypothyroidism) 22. 
• A 2020 clinical trial involving patients with hypothyroidism found that a combination of probiotics and prebiotics (which stimulate probiotic growth) reduced the need for levothyroxine after eight weeks 23. It also led to improvements in fatigue. 
• Probiotics help to fight H. pylori and small intestine bacterial overgrowth (SIBO), which are associated with thyroid dysfunction 24 25. 

Most probiotics are likely to be helpful, but in my clinical experience, the best results come when using a triple probiotic therapy of Lactobacillus & Bifidobacterium blend, Saccharomyces boulardii (a friendly yeast), and soil-based probiotics. 

Each of these categories has its own benefits but the three types of probiotics work together for the most balanced, comprehensive support. 

Other Important Nutrients

With some important exceptions (folic acid, omega-3s, etc.) supplements aren’t recommended during pregnancy, so you should look to get what you need from a balanced diet. For example, it’s easy to get enough selenium and inositol from your food by looking at the two charts below. 

Getting enough of these two nutrients is important because 26:

• Selenium can help activate thyroid hormones.
• Inositol may help improve the thyroid gland’s responsiveness to TSH.

While many people overdo it on iodine, pregnant women are one of the few populations that are more susceptible to an iodine deficiency. The Endocrine Society guidelines recommend that women of childbearing age should have an average iodine intake of 150 μg/day, which should be increased to 250 μg/day during pregnancy and breastfeeding 27.

The most recent guidelines issued by the American Thyroid Association suggest that all pregnant women should add a daily oral supplement of 150 μg of iodine to their diet 28. 

You should always talk to your own doctor before taking iodine supplements as a number of studies have shown excess iodine may also actually be bad for hypothyroid conditions 29 30 31. This is particularly important if you are not pregnant and are trying to conceive, as excess iodine intake could affect your thyroid and fertility. 

However, the link between excess iodine and hypothyroidism hasn’t been directly studied in pregnancy. Low iodine intake while pregnant is significantly associated with poor fetal development, so you shouldn’t restrict iodine intake on your own. The amount of iodine included in a prenatal vitamin is often very safe (be sure to always check the label) and is just enough to meet the daily requirement.

Pregnancy Hypothyroidism: A Special Case

When it comes to overt and subclinical hypothyroidism (high TSH) and pregnancy you’ll likely need to take levothyroxine to avoid any potential risks to your baby’s healthy development. Women who are trying to become pregnant may also benefit from thyroid medication.

Regardless of whether you have a history of hypothyroidism, it’s essential to check and monitor your TSH levels once you become pregnant. It’s also a good idea to support these medications with a gut-healthy, nutrient-rich diet and a probiotic supplement.

If you need more personalized help with issues surrounding conception, pregnancy, and thyroid health, you may benefit from a consultation with one of our experienced practitioners at the Ruscio Institute for Functional Medicine. 

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.