Can you take levothyroxine during pregnancy?

In this article:

• Hypothyroidism during pregnancy
• Levothyroxine while pregnant
• Pregnancy dosage
• Potential risks
• Alternatives
• Natural remedies

In this article

• Hypothyroidism during pregnancy
• Levothyroxine while pregnant
• Pregnancy dosage
• Potential risks
• Alternatives
• Natural remedies

About 30 million adults in the U.S. have an underactive thyroid, which means their thyroid gland doesn’t produce enough thyroid hormones to keep up with the body’s demands. Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates your thyroid to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3). T3 and T4 are responsible for regulating your metabolism, body temperature, growth, and energy levels. When thyroid dysfunction causes a hormonal imbalance, you may develop a thyroid disorder such as hyperthyroidism (overproduction of thyroid hormones), hypothyroidism (underproduction of thyroid hormones), or thyroid autoimmunity (autoimmune thyroid disease, or AITD).

Hypothyroidism is usually treated with prescription medications like levothyroxine, a synthetic thyroid hormone treatment that mimics T4. Levothyroxine is the first-line treatment for hypothyroidism. But what happens if you have an underactive thyroid during pregnancy when you have to be especially cautious about the medications you take to avoid pregnancy complications like preterm birth and pregnancy loss?

It happens more often than you might think, according to Libu Varughese, MD, endocrinologist and medical adviser for Aeroflow Diabetes. Hypothyroidism occurs more often in women. It’s not uncommon for pregnant women to have it. It occurs in about 2% to 3% of pregnancies. The good news is that it’s generally considered safe and necessary to use levothyroxine for thyroid problems. Here’s why—and what you can expect if you need to use this medication while pregnant.

Hypothyroidism during pregnancy

Women can have hypothyroidism pre-pregnancy or may develop pregnancy-related hypothyroidism. Both mother and fetus need to have sufficient thyroid hormone levels during pregnancy. Expectant mothers who have hypothyroidism may experience anemia, preeclampsia, hypertension, placental abruption, and postpartum hemorrhage.

Thyroid hormones are also important to the fetus’s growth and development, especially its neurological system, playing a crucial role in how the fetal brain forms and develops during pregnancy. Babies born to mothers with untreated hypothyroidism during pregnancy are more likely to have irreversible cognitive disabilities, as shown in studies like this review, which found that moderate hypothyroidism during pregnancy (particularly in the first trimester) is associated with cognitive impairments in children born to mothers with hypothyroidism.

Untreated hypothyroidism in pregnancy is also associated with poor birth outcomes, including miscarriage, low birth weight, and preterm delivery. It also puts the pregnant person at an increased risk of gestational hypertension or high blood pressure during pregnancy.

Can you take levothyroxine while pregnant?

Levothyroxine therapy is not only safe, but it’s the most commonly recommended medication used to treat hypothyroidism during pregnancy, Dr. Varughese explains. Because it’s a synthetic version of the same thyroid hormone your body naturally makes, it helps restore normal thyroid function without unwanted side effects.

Levothyroxine has a long history of safe use in pregnancy, says Rikki Baldwin, DO, OB-GYN with Memorial Hermann Medical Group in Texas. It is the gold standard for the treatment of hypothyroidism during pregnancy, called maternal hypothyroidism. In fact, it improves birth outcomes. A review of studies found that levothyroxine lowered the risk of miscarriage and newborn death associated with low thyroid levels during pregnancy.

While hypothyroidism can occur at any stage of pregnancy, it’s most dangerous when onset is in the first trimester. Hypothyroidism occurring in the second trimester or third trimester is still associated with risks, but they are less severe.

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Levothyroxine dosage during pregnancy

Your body typically has a higher demand for thyroid hormones during pregnancy, says Dr. Baldwin. This demand can increase as your pregnancy progresses. That means your pre-pregnancy dose (or starting dose if you’re diagnosed during pregnancy) of levothyroxine may need to increase for the nine months you’re expecting.

Maternal hypothyroidism encompasses two types of hyperthyroidism: overt hypothyroidism, characterized by clinically elevated TSH levels and low T4 levels, and subclinical hypothyroidism, with elevated TSH and normal T4 levels. Thyroid function tests performed by an endocrinology specialist can distinguish between the two forms. You may undergo the following tests:

• TSH tests measure the levels of thyroid-stimulating hormones in your blood or serum TSH).
• Thyroid blood tests (TSH, T3 and T4, thyroglobulin uptake test, and thyroid antibodies) check your blood for hormones and proteins like thyroxine, thyroid peroxidase antibodies, and thyroglobulin to determine if you have hypothyroidism or hyperthyroidism.
• Thyroid imaging tests use radioactive iodine to take an image of your thyroid. The scan provides further information about your thyroid function.

Always consult a healthcare professional for a definitive diagnosis. Your healthcare provider can help you determine the right treatment for your thyroid needs. Dr. Baldwin says your hormone levels can be checked every trimester to determine if your hypothyroidism is well-controlled on levothyroxine. Still, if your hormone levels are changing or your medication dosage is being slowly increased to meet your body’s needs, you will likely need to have your thyroid hormone levels checked every four to six weeks.

You should also expect dosage changes again after you give birth, says Dr. Baldwin: “During the postpartum period, your dose of levothyroxine can be decreased to pre-pregnancy levels, with hormone levels checked about two months after delivery.”

What are the risks of taking levothyroxine while pregnant?

Levothyroxine is safe for mothers and their growing babies during pregnancy. Pregnant women typically don’t experience side effects from levothyroxine unless they are on too much or too little of the medication, says Dr. Varughese.

Though levothyroxine does cross the placenta and enter the fetus’s bloodstream, this is actually a good thing. Growing fetuses need the right amount of thyroid hormone to be passed on from their mothers in utero, so when the mother’s thyroid hormone levels are deficient, a fetus may not get enough thyroid hormones to develop properly.

Dr. Baldwin notes that some scientific literature suggests the possibility of an increased risk of gestational diabetes, taking levothyroxine during pregnancy, but also emphasizes that this complication is more likely to occur in women with untreated hypothyroidism during pregnancy.

In other words, the benefits of taking levothyroxine far outweigh the risks since not treating an underactive thyroid during pregnancy is more dangerous than taking the medication.

What can I take instead of levothyroxine during pregnancy?

Levothyroxine is the only medication recommended to treat underactive thyroid in pregnancy, according to Dr. Varughese. Not only does it have a well-studied safety profile, it effectively boosts a fetus’s thyroid levels in ways other medications can’t.

For example, the most common alternative, Armour Thyroid (non-synthetic natural hormone derived from pigs), is sometimes used to treat hypothyroidism, but Dr. Varughese says it’s unsuitable for pregnant women because of its variable hormone content. It contains more T3 than T4, which is a problem for unborn babies; they can’t utilize T3 in utero, so they need a steady supply of T4 from their mothers for their brains to develop properly. Without enough T4, a fetus could be hypothyroidic even if the mother’s thyroid hormone levels appear to be high enough.

Natural remedies for thyroid control during pregnancy

People with an underactive thyroid need medication to get their thyroid hormone levels back to normal. Hypothyroidism is caused by a failure of the thyroid gland to function correctly, says Dr. Varughese, so the best way to replace the deficient levels of hormone is with hormone replacement therapy medication.

It’s not recommended, Dr. Varughese adds, to try and manage hypothyroidism without medication like levothyroxine—especially during pregnancy, when sufficient thyroid levels are so important for the baby’s growth and development. However, that doesn’t mean you can’t take medication and boost your thyroid in other ways during pregnancy.

• Make sure you get enough iodine in your diet. This mineral helps the thyroid function correctly. Iodine-rich foods include dairy, eggs, cereal, lean poultry, iodine-enriched table salt, and seafood.
• Take a prenatal vitamin containing at least 150 micrograms of iodine.
• Avoid taking levothyroxine at the same time as your prenatal vitamin; most prenatal vitamins contain nutrients like calcium and iron, which can affect how well your body absorbs your medication.
• Avoid taking levothyroxine while consuming soy-based foods, like tofu and edamame, which can also interfere with the medication’s absorption.

While these tips are generally safe for most people to use, it’s important to always discuss any home remedies or other therapies with your healthcare provider before trying them, especially if you’re pregnant.