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High TSH Levels and Fertility: What You Need to Know

Written by Dr. Michael Ruscio, DC on October 3, 2022

Written by Dr. Michael Ruscio, DC on October 3, 2022 — Reviewed by Dr. Hannah Hamlin

• TSH and Thyroid Basics|
• High TSH Levels and Fertility|
• High TSH Levels and Pregnancy |
• Treating High TSH Levels|
• The Bottom Line|

If you’re trying to get pregnant, but it’s just not happening, you may want to speak with your doctor about having your thyroid-stimulating hormone (TSH) level checked. TSH tells your thyroid gland to produce thyroid hormones, which are essential for fertility, maintaining a pregnancy, and a baby’s development. Generally speaking, high TSH levels alone aren’t cause for concern, but for women who are hoping to conceive and those who are already pregnant, high TSH levels can negatively affect fertility and pregnancy outcomes. 

The good news is, it IS possible to get pregnant and have a healthy pregnancy if you do have thyroid issues. The more you know about what’s going on, the more you can address it and move on to have a healthy pregnancy.

In this article, we’ll break down what you need to know about TSH levels and fertility, and share a simple formula you can use to determine if you have thyroid problems that warrant treatment with medication. We’ll also dive into the specific concerns related to high TSH levels, fertility, and pregnancy. 

We will compare how high TSH levels are assessed, treated, and monitored when you are trying to conceive versus once you are pregnant. And, lastly, we will share the natural therapies (like improving gut health, managing stress, and dietary supplementation) that can be used to address high TSH levels while trying to conceive.

TSH and Thyroid Basics

TSH, or thyroid-stimulating hormone, is produced by the pituitary gland (a pea-sized endocrine gland in your brain) to signal the thyroid gland (an endocrine gland located in your neck) to produce two thyroid hormones 1:

• T3 (triiodothyronine)
• T4 (thyroxine)

If T3 and T4 levels drop, the pituitary gland responds by secreting more TSH, which brings thyroid hormone levels back to normal. On the other hand, if T3 and T4 levels are elevated, the pituitary gland cuts back on TSH production 1.

When high TSH levels are accompanied by low thyroid hormone, it may cause the following symptoms of hypothyroidism 2:

• Weight gain
• Cold intolerance
• Fatigue
• Shortness of breath
• Hoarseness of voice
• Decreased taste, vision, or hearing
• Impaired memory
• Impaired mood
• Pins and needles sensation (paresthesia)
• Constipation
• Muscle weakness, cramps, and joint pain
• Bleeding
• Dry skin
• Hair loss
• Kidney diseases

But, more importantly, when high TSH levels are a result of hypothyroidism, it can affect your menstrual cycle, fertility, and ability to maintain a pregnancy. 

What Do High TSH Levels Mean?

TSH levels naturally fluctuate throughout the day, and are often higher in the morning and lower in the late afternoon/mid-evening 3. However, persistently high TSH levels (while often innocuous) may indicate that your thyroid hormone production is too low 1 4. To help you figure out where your own thyroid levels fit into, we will look at the three general categories to consider when it comes to high TSH 1:

1. Primary (or overt) hypothyroidism (high TSH levels coupled with low free T4 levels) indicates an underactive thyroid gland and is most often caused by Hashimoto’s thyroiditis (an autoimmune disease). Your thyroid gland isn’t producing enough thyroid hormone in this case.
2. Subclinical hypothyroidism (high TSH coupled with normal free T4 levels) is less severe and isn’t always indicative of a true thyroid problem.
3. Secondary hyperthyroidism (very high TSH, free T3, and free T4 levels) is very rare and is usually due to a tumor in the pituitary gland or hypothalamus (a part of the limbic system in the brain).

In general, having a high TSH level on its own shouldn’t necessarily sound the alarm. You may need to have additional thyroid function tests (like T3 and T4) to determine if there’s an actual medical condition to address.

With that in mind, everyone who is diagnosed with overt hypothyroidism will likely require medication, while those who fall in the subclinical category typically do not. However, there are two populations (which we will cover in a moment) who are an exception to this rule — women who are trying to conceive or who are pregnant should be treated for subclinical hypothyroidism.  

How High is Too High?

Much confusion exists when it comes to TSH levels. While many in the integrative medicine community promote a more narrow reference range for TSH, research tells us that the standard range of 0.45 to 4.5 mIU/L is clinically valid and can be used (along with free T4 levels) to diagnose thyroid disorders 5.

There are a few caveats to this rule though:

• Patients with hypothyroidism (low thyroid or underactive thyroid) who are receiving thyroid hormone replacement should aim for optimal TSH levels of 2.5 mIU/L 6.
• People over the age of 70 should be assessed using an age-appropriate range since TSH levels tend to rise with age. The American Thyroid Association suggests a target range of 4.0 to 6.0mIU/L in people aged 70 to 80 7. 
• In pregnant women, TSH levels decline in the first trimester due to a rise in the hormone, human chorionic gonadotropin (hCG), and rise again after 10 to 12 weeks of gestation, so the range is adjusted 8. 

High TSH Levels and Fertility

If you’re struggling with getting pregnant, it’s important to have your thyroid function assessed. 

Whereas it’s well-accepted that untreated overt hypothyroidism can result in fertility troubles, things are less clear when it comes to subclinical hypothyroidism 9 10 11. One observational study found elevated TSH levels to be associated with a decreased pregnancy rate 12, and another found women with unexplained infertility to have significantly higher TSH levels 13. 

Treatment of high TSH levels in both overt and subclinical hypothyroidism seems to improve fertility outcomes:

• Two randomized controlled trials found infertile women with subclinical hypothyroidism who underwent assisted reproduction (such as IVF) had improved embryo quality, implantation rate, and live birth rate when given levothyroxine (Synthroid) 14.
• Another study found that 76.6% of women treated for overt and subclinical hypothyroidism were able to conceive after treatment with thyroid hormone replacement 15.

While the research suggests a connection, there needs to be more studies to better understand TSH levels and fertility. That being said, when weighing the pros and cons of treating high TSH for fertility, the benefit of successfully conceiving seems to far outweigh the risk of being on unnecessary medication for many women. 

Additionally, starting medication while trying to conceive may be temporary, as TSH levels can significantly change (and normalize) postpartum and subclinical hypothyroidism often doesn’t require medication after pregnancy. 

Regardless, it’s up to you and your doctor to decide if medication is the best route for your elevated TSH levels. Now let’s move on to how thyroid dysfunction could impact you once you’re pregnant.

High TSH Levels and Pregnancy

The prevalence of hypothyroidism is fairly uncommon in pregnancy (0.3% to 0.5% of pregnant women deal with this condition), but this is nevertheless a time when we should be meticulous with thyroid assessment and is one of the few exceptions when normal fluctuations in TSH levels can be consequential 9. 

There’s a clear association between untreated overt hypothyroidism and the following negative pregnancy outcomes 8 9:

• Miscarriage
• Preterm delivery
• Preeclampsia (high blood pressure)
• Maternal hypertension
• Postpartum bleeding
• Low birth weight
• Stillbirth
• Impaired intellectual functioning of the fetus
• Impaired brain development of the fetus 

While the research is somewhat mixed on optimal TSH levels in pregnancy, one study found women with TSH levels greater than 2.5 mIU/L had a significantly increased risk of miscarriage when compared to women with TSH levels of 0.1 to 2.5mIU/L 16. Providing thyroid hormone replacement to women with TSH levels greater than 2.5mIU/L significantly reduced the miscarriage rate 16. 

Other studies haven’t found an increased risk of miscarriage or difference in pregnancy outcomes when TSH levels were 2.5 to 4.5mIU/L, but miscarriage risk almost doubled when TSH levels were 4.51 to 10mIU/L and practically quadrupled when TSH levels were greater than 10mIU/L 17 18. 

In contrast to the general population, women with subclinical hypothyroidism may also experience poor pregnancy outcomes 11.  Women in this group have been found to have an increased risk of 19 20 21:

• Pregnancy loss
• Placental abruption
• Premature rupture of membranes
• Neonatal death
• Preeclampsia
• Preterm birth

Thankfully, high TSH levels can be treated with thyroid medication both in women who are planning for a baby and who are already pregnant. Let’s look further into high TSH levels and fertility, and see how treating hypothyroidism varies between women who are preconception and who are currently pregnant.

Treating High TSH Levels

If you’re not pregnant or planning to conceive, having a high TSH level may not be a problem. In fact, subclinical hypothyroidism spontaneously remits back to normal with no treatment up to 50% of the time 22 23 24 25 26 27. 

But there are a few scenarios where thyroid hormone replacement is likely necessary:

• Primary hypothyroidism (pregnant or not) 28 29.
• Subclinical hypothyroidism accompanied by thyroid antibodies (thyroid peroxidase or TPO) and/or TSH levels above 10mIU/L 27.
• Women with subclinical hypothyroidism who are pregnant or planning to become pregnant 10 11 15 30 31 32 33.

Treatment Options for High TSH Levels: Fertility and Pregnancy

Though treating high TSH levels is necessary for both pregnant women and those hoping to conceive, there are slight differences in the approach. The following chart provides an overview of the testing frequency, goal TSH levels, and treatment options for women with hypothyroidism:

Testing and Monitoring

For women with hypothyroidism who are trying to conceive, TSH can be checked every three to four months. But since TSH levels can naturally vary throughout pregnancy, pregnant women with hypothyroidism need to have a TSH blood test every six weeks in order to catch and treat any higher than optimal levels. 

For pregnant women without thyroid disease, TSH screening frequency should be determined by their symptoms and their healthcare provider. 
Regarding optimal TSH levels, women trying to conceive can use the normal range of 0.45 to 4.5mIU/L. But this range is modified for those who are already pregnant — I prefer to use the following TSH level guidelines from the American Association of Clinical Endocrinologists for pregnant women to avoid potentially negative pregnancy outcomes 8:

Treating high TSH levels quickly in women trying to conceive and pregnant women can significantly improve outcomes, so let’s take a look at treatment options.

Treating High TSH Levels With Medication

Since there’s a connection between TSH levels and fertility, women with subclinical hypothyroidism who are trying to conceive may need to be treated with thyroid hormone replacement. 

The American Thyroid Association and the American Association of Clinical Endocrinologists do NOT recommend the use of desiccated (natural) thyroid or T4+T3 combination therapy in pregnant women or those who are planning to become pregnant as both can lower serum levels of thyroid hormone and potentially impair a developing fetus 8. 

If you’re pregnant and being treated for a thyroid condition with these medications, it’s important to speak to your healthcare professional about switching to T4 (levothyroxine), which has been shown to improve pregnancy and miscarriage rates in women with a TSH greater than 4.0 mIU/L 11.

Pregnant women with overt hypothyroidism (high TSH coupled with low free T4) must be treated with thyroid hormone to prevent negative pregnancy outcomes. And while the research on subclinical hypothyroidism in pregnancy is mixed, the overall benefits seem to far outweigh the risks. Treating with levothyroxine reduces the risk of 30 31 32:

• Pregnancy loss 
• Preterm birth
• Gestational hypertension
• Abortion
• Postpartum hemorrhage
• Low birth weight

Too Much Thyroid Medication

The possibility exists that anyone on thyroid medication could become over-medicated. This is a higher risk in pregnancy because TSH levels naturally fluctuate. Too much thyroid hormone can suppress levels of TSH (leading to an overactive thyroid), double the odds of having a preterm delivery, and lead to preeclampsia and decreased birth weight 10 34. 

This is why is so important to get your TSH levels regularly checked during pregnancy — especially while taking thyroid medication. 

If you have a high TSH level, you’ll want to work with your provider to determine the best course of treatment. And always check with your provider before making any changes to or stopping your current medication regimen.  

Treating High TSH Levels and Fertility With Natural Therapies

There are several natural therapies to consider in the context of high TSH levels and fertility (and pregnancy). While pregnant women will need to be more cautious with diet therapy, supplements, and exercise, women trying to conceive have a wide variety of options:

Gut health: 

In my experience, a small percentage of ‘thyroid patients’ will discover that their 

TSH levels completely normalize once their gut issues (gut infections, intestinal permeability, imbalances of the microbiome, etc.) have been treated and they can discontinue thyroid medication 35 35 36 37. Others do need to continue with thyroid hormone replacement, which — after healing the gut and reducing symptoms — can be optimized. Addressing gut health can safely be accomplished prior to conception, and we provide a step-by-step guide in Healthy Gut, Healthy You.

Diet therapy:

Several diets have been found to be helpful for high TSH levels and/or hypothyroidism. A low-iodine diet may completely resolve hypothyroidism and an elimination, gluten-free (for those with celiac or gluten sensitivity), and/or lactose-free (in the lactose intolerant) diets can significantly improve TSH levels 38 39 40 41. When it comes to diet therapy for pregnant women, you’ll want to avoid overly strict diets and iodine restriction. However, the Paleo diet is a healthy option that’s not overly restrictive and is fairly easy to implement. 

Dietary supplements:

Many dietary supplements for your thyroid are safe for those trying to conceive. However, if you are pregnant and are trying to treat your TSH levels naturally, many supplements are harmful to a developing fetus (such as DHEA), and you should consult with your functional medicine practitioner first

Below is a chart of the dietary supplements that may improve TSH levels in non-pregnant women:

Stress management: 

Fertility issues can be very stressful. If you’re trying to conceive, a daily stress management technique can help to restore a healthy stress response, which will go a long way toward improving gut and thyroid function. Meditation, yoga, walking in nature, spending quality time with loved ones, and deep breathing are all great options.

Sleep:

Disrupted sleep can increase inflammation and lead to hormonal imbalances. Set the foundation for healthy sleep by first creating a healthy sleep routine with the goal of 7 to 8 hours of restful sleep per night. Avoid blue light (from your TV, smartphone, or computer) and large meals before bedtime, and sleep in a dark, cool, quiet environment.  Exercise and meditation may also improve sleep quality.

It’s worth repeating that pregnant women with overt or subclinical hypothyroidism need to use discretion with natural therapies. Always speak with your provider and err on the side of caution with overly strict diets, supplements, herbal preparations, and rigorous exercise (or when starting a new exercise regimen).

High TSH Levels and Fertility Problems Improve with Medication and Natural Therapies

If you’re planning to become pregnant or are pregnant, it’s important to speak with your primary care provider about your TSH test results and have your TSH levels (and possibly other thyroid levels) monitored routinely. 

You’ll definitely need to implement thyroid hormone medication if your thyroid function tests confirm overt hypothyroidism, and potentially if you have subclinical hypothyroidism. Thyroid hormone replacement has been shown in both cases to improve pregnancy and fertility outcomes, and the benefits seem to far outweigh any risks. 

Women trying to conceive can also employ many natural therapies including diet changes, supplements, stress management techniques, exercise, and sleep hygiene to improve their thyroid function and their chance of getting pregnant. Women who are already pregnant need to be more cautious when it comes to some of the natural therapies and should speak to their provider before adding things like strict dieting or supplements.

If you would like a more comprehensive plan, we’ve just launched our complete thyroid self-help program, which is loaded with tools to empower you to take control of your thyroid health. If you’re not a do-it-yourselfer, the Ruscio Institute for Functional Health is available as well.

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.