Dr. Cindy Duke, MD, PhD answers the most common questions about thyroid problems

Reviewed by Health Guide Team, 

Written by Chanel Dubofsky 

Reviewed by Health Guide Team, 

Written by Chanel Dubofsky 

last updated: May 06, 2020

7 min read

How important is the thyroid gland? The answer, simply put, is super important. "It's your 'get up and go,' says Dr. Cindy Duke, MD, PhD who is board certified in obstetrics and gynecology and has a fellowship trained in reproductive endocrinology and infertility (REI). "Even if you're not currently pursuing pregnancy, the thyroid plays such a critical role that it should be at its peak function,” she explains.

Your thyroid, which is part of the endocrine system, controls your hormone production, as well as the function of your metabolism, your nervous system, and your menstrual cycle (ergo, your fertility). Here, we recap our recent virtual info session on Demystifying Your Thyroid with Dr. Duke.

After you’re done reading this article (and watching the video at the end if you’re feeling extra curious), you’ll have the answers to these Q’s:

  • What are hyperthyroidism and hypothyroidism?

  • What tests can clue you in to thyroid disorders?

  • Is it possible to treat hypothyroidism naturally?

  • Are there any dietary restrictions or foods to avoid for women with hypothyroidism?

  • How can thyroid disorders impact conception?

  • Is it safe to try to conceive while treating a thyroid disorder?

  • How can thyroid disorders impact pregnancy?

  • How can you stay on top of your thyroid before and during pregnancy?

Modern Fertility

Get proactive about your reproductive health

What are the common problems with your thyroid?

The main hormone generated by your thyroid is thyroxine (T4), and when there's too much or too little of it, health problems can occur. If you're secreting too much thyroxine, you have an overactive thyroid, or hyperthyroidism. If you're not secreting enough, you have an underactive thyroid, known as hypothyroidism.

Symptoms of an underactive thyroid can include heavier menstrual bleeding, weight gain, and depression — and there is also a relationship between a hypoactive thyroid and polycystic ovary syndrome (PCOS). Symptoms of an overactive thyroid can include unexplained weight loss, increased appetite, feelings of nervousness and anxiety, difficulty sleeping, fewer or lighter menstrual cycles, increased sweating, and heat intolerance.

The hormone calling the shots in terms of your brain’s production of T4 is called thyroid-stimulating hormone, or TSH. "TSH is how your brain talks to your thyroid," explains Dr. Duke. If your TSH level is above 4.5 mIU (milli international units), your thyroid is underactive — if it’s under 1.0, or close to 0, it's overactive.

Subclinical hypothyroidism is when you're in between: above 2.5, but not 4.5. If your TSH isn't 0, but it's not above 1, that's indicative of subclinical hyperthyroidism. In both subclinical hyperthyroidism and hypothyroidism, your thyroid hormone levels aren’t “exactly in the normal range for things like ovulation and hormonal function in the ovaries,” Dr. Duke explains. “[The thyroid is] doing the work… sort of.”

What tests can clue you in to thyroid disorders?

Both hypo/hyperthyroidism are diagnosed via physical exam and a blood test that evaluates your TSH levels. If your test reveals high levels of T4 and low to nonexistent amounts of TSH, you have an overactive thyroid. Low levels of T4 and high levels of TSH indicate an underactive thyroid. After your diagnosis, your doctor may pursue other testing to figure out why your thyroid is over or underactive.

If you have a known thyroid dysfunction, your doctor will also check your TSH level. “If your levels are lower than 3.5 [and you’re thinking about having kids], I'll follow up with a test to check for antibodies because I'm looking for risks for your pregnancy,” Dr. Duke explains. “If you're someone with a history of recurrent miscarriages and your TSH is under 4.5, but you have thyroid antibodies, that's something I want to know about so I can take some steps for you."

Some tests will evaluate your TSH level, as well as your fT4 level if your TSH results suggest thyroid dysfunction. Your body has two kinds of T4 — free, which travels into tissues, and bound, which attaches to proteins and prevents the free version from entering those tissues. If the ratio of bound to free is too high or too low, that can also indicate hypo/hyperthyroidism — and measuring your fT4 level can give you insight into that ratio.

Is it possible to treat hypothyroidism naturally?

TPO (thyroid peroxidase) is an enzyme that's important in the production of thyroid hormone. If you have TPO antibodies, your autoimmune system is activated and your white blood cells attack your body, causing impaired thyroid function. If you have Graves’ disease, a type of overactive thyroid, your immune system makes antibodies that attack the thyroid, which impacts your TSH and can impair thyroid function. Hypothyroidism is often treated with daily use of the synthetic thyroid hormone levothyroxine, an oral medication that restores your hormone levels and reverses your symptoms.

If you'd like to reduce TPO antibodies naturally, advises Dr. Duke, "Try not to activate your immune system by doing things that you know can cause allergic responses. If you're sensitive to certain foods, like dairy, now is the time to cut those foods out."

Are there any dietary restrictions or foods to avoid for women with hypothyroidism?

"If you're someone who has a plant-based diet, or with an underlying autoimmune disease, it's important to know that soy and dairy products can have an impact on your thyroid function and activate your inflammatory system," says Dr. Duke.

"If you're practicing a salt-free diet, you will need some iodine added to your diet, so you should be eating mushrooms, prunes, some kinds of seafood — foods we know have iodine in them. You might also need to have a tincture of iodine, a drop under your tongue a couple of times per day so you're getting enough."

How can thyroid disorders impact conception?

Both hyperthyroidism and hypothyroidism have been linked to abnormal menstrual cycles, which can make predicting ovulation difficult to impossible — therefore impeding conception. One study, released in 2015, concluded that the preconception levels for TSH should be equal to or greater than 2.5 mIU to avoid fertility or pregnancy complications.

Getting a handle on your thyroid through treatment can reduce the chances of related fertility issues down the line. In one study of a group of almost 400 women suffering from infertility, 24% of participants were found to have hypothyroidism — but within a year of treatment, 76% were able to conceive.

Male fertility can also be impacted by hyper and hypothyroidism. "You can see lower semen volume, changes in sperm density, how the sperm moves, and the type of sperm being formed in terms of its size and shape," says Dr. Duke. If sperm abnormalities are detected in a semen analysis, doctors will conduct a more thorough investigation, including taking a look at thyroid function.

Is it safe to try to conceive while treating a thyroid disorder?

Hypothyroidism (as well as  enlarged thyroids and thyroid cancer) is treated with a synthetic thyroid, often known as Levothyroxine or L-Thyroxin. Armour Thyroid, a brand of synthetic thyroid hormone, is also used to treat hypothyroidism.

According to Dr. Duke, there's no reason to be concerned about synthroid impacting your fertility unless you're overdosing. "You should have enough TSH, but not so much that it's shutting down your ovarian response,"  she says. "The dosing of Armour Thyroid is different from that of L-Thyroxin, but it's also safe to use while pregnant," says Dr. Duke. (An important note: If you have a dairy allergy, you might not feel better when taking a thyroid medicine, since some do contain it, so check this out with your doctor.)

Hyperthyroidism can be treated with radioactive iodine (if you opt for this, you'll be advised to wait until six months after treatment has ended before trying to conceive), and antithyroid medications like methimazole (Tapazole) and propylthiouracil, which are safe to take before and during pregnancy (propylthiouracil is preferable if you're pregnant since Tapazole can lead to congenital defects), and removal of the thyroid.

One more thing: If you're going off hormonal birth control for the purposes of trying to conceive, Dr. Duke advises keeping in mind the reasons you went on it in the first place. Was it to prevent pregnancy, or deal with symptoms of a condition such as PCOS (polycystic ovary syndrome)?  

"Depending on why and what birth control you've been on, it may take up to a year to get pregnant, and you may need help ovulating." She advises tracking your ovulation, exercising, and looking at what causes your flare-ups, or periods when the one or more symptoms of Hashimoto's get worse, such as changes in diet.

How can thyroid disorders impact pregnancy?

It is possible to get pregnant if you have a thyroid condition, but if it's untreated, there are risks to yourself and your baby. If you have untreated hypothyroidism and you're pregnant, but not being treated, you could experience miscarriage, stillbirth anemia, preeclampsia (that's high blood pressure that happens after 20 weeks and can lead to organ failure and premature birth), as well as myxedema, which can result in coma or death. In babies, untreated hypothyroidism can cause low birth weight, as well as problems with nervous system and brain development, and thyroid problems.

When it comes to hyperthyroidism in pregnancy, the most common cause is Graves' disease. Untreated Graves’ in pregnancy can result in early labor, as well as preeclampsia, and what's known as a thyroid storm, in which your blood pressure, temperature, and heart rate all skyrocket. "This is one of the top three obstetric emergencies we face," says Dr. Duke. "If it's not dealt with in a matter of hours, there can be really detrimental outcomes."

Risks to the baby from untreated hyperthyroidism include low birthweight, fast heart rate, birth defects, and fetal hyperthyroidism.

And if you don't have a thyroid at all? "For someone who doesn't have a thyroid or someone whose thyroid is inactive, it's critically important to be on thyroid hormone," says Dr. Duke, "but you need to be at that sweet spot, meaning your TSH should not be undetectable, and your thyroxine can't be too low. What I recommend is to go back to your doctor and tell them you're trying to get pregnant, and they'll adjust your thyroid meds accordingly so you can get pregnant and stay pregnant and have the best outcome for your baby."

How can you stay on top of your thyroid before and during pregnancy?

When preparing your body for pregnancy, Dr. Duke recommends antioxidants, which help cells process energy better, to all her patients. For Hashimoto's, an autoimmune disorder that can cause underactive thyroid combined with PCOS, she recommends 2000 milligrams (mg) per day of the supplement myo-inositol. "The key with Hashimoto's is getting your thyroid function back to normal, figuring out your triggers ... and getting those under control, and getting active,” she says. “Endorphins can change how the body responds to hormones."

And prenatal vitamins? "Your prenatal should have the basics," says Dr. Duke, "and you should also look at your triggers and make sure it doesn't have any of those. Some prenatals have dairy in them, so if that's your trigger, you want to avoid that." Prenatals should have folic acid (at least 400 micrograms, or mcg), methylfolate, and iron.

If you're on thyroid medication, Dr. Duke stresses the importance of checking in with your thyroid throughout pregnancy. "The fetal brain [and] spinal cord start forming at around 21 days, and the pregnancy hormone can actually activate your thyroid,” she explains. “So, sometimes medicine needs to be tweaked in the first trimester. I check it with the first pregnancy test, and then once per trimester, and at delivery."You can listen to the entirety of Dr. Duke's webinar here, and stay tuned to Modern Fertility for more opportunities to get your reproductive health questions answered by the experts!


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

May 06, 2020

Written by

Chanel Dubofsky

Fact checked by

Health Guide Team

About the medical reviewer