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What Causes Low Thyroid Levels In Pregnancy

How Is Hypothyroidism Treated During Pregnancy

HYPOTHYROIDISM EXPERIENCE & DIAGNOSIS – Pregnancy, Postpartum and Low Thyroid Issue

Thyroid hormone replacement is used to treat the mother. Dosage of thyroid hormone replacement therapy is based on the individual’s levels of thyroid hormones. Thyroid hormone levels may change during pregnancy. And, the thyroid replacement dosing may also change. Thyroid hormone levels need to be checked every 4 weeks during the first half of pregnancy. The treatment is safe and essential to both mother and fetus. Routine screening for all newborns includes a test of thyroid hormone levels.

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What Is The Link Between Iodine Deficiency And Thyroid Function In Pregnancy

Having too little iodine in your body is a common cause of low thyroid hormone levels. A study found that, on average, Australian women consume 100 micrograms of iodine a day. However, the World Health Organization recommends a daily intake of least 250 micrograms of iodine during pregnancy and breastfeeding.

Australian guidelines recommend that pregnant and breastfeeding women take a supplement containing 150 micrograms of iodine each day .

Check with your antenatal health provider if you are concerned about your iodine levels, particularly if you are taking supplements such as pregnancy or pre-natal vitamins and minerals.

Your pharmacist will also be able to guide you on the potential impact of your prescription and over-the-counter medicines and their potential impact on iodine absorption and thyroid function.

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How Do Doctors Treat Hypothyroidism During Pregnancy

Treatment for hypothyroidism involves replacing the hormone that your own thyroid can no longer make. Your doctor will most likely prescribe levothyroxine, a thyroid hormone medicine that is the same as T4, one of the hormones the thyroid normally makes. Levothyroxine is safe for your baby and especially important until your baby can make his or her own thyroid hormone.

Your thyroid makes a second type of hormone, T3. Early in pregnancy, T3 cant enter your babys brain like T4 can. Instead, any T3 that your babys brain needs is made from T4. T3 is included in a lot of thyroid medicines made with animal thyroid, such as Armour Thyroid, but is not useful for your babys brain development. These medicines contain too much T3 and not enough T4, and should not be used during pregnancy. Experts recommend only using levothyroxine while youre pregnant.

Some women with subclinical hypothyroidisma mild form of the disease with no clear symptomsmay not need treatment.

If you had hypothyroidism before you became pregnant and are taking levothyroxine, you will probably need to increase your dose. Most thyroid specialists recommend taking two extra doses of thyroid medicine per week, starting right away. Contact your doctor as soon as you know youre pregnant.

Your doctor will most likely test your thyroid hormone levels every 4 to 6 weeks for the first half of your pregnancy, and at least once after 30 weeks.1 You may need to adjust your dose a few times.

Understanding Reference Ranges During Pregnancy

Thyroid Disease and Getting Pregnant

When we talk about reference ranges it’s important that you understand what exactly they mean.

A reference range is created by local lab testing companies.

These numbers are supposed to represent the average numbers of all people in your local area.

Lab companies create these ranges by taking information and lab results from thousands of people and then aggregate the data using statistical analysis to create the reference ranges .

The goal of these ranges is to include 95% of the population within the ranges provided.

This means that 2.5% of people tested fall below the reference range and 2.5% of people fall higher than the range provided.

This idea is very important, especially when it comes to pregnancy and TSH testing.

The reference ranges provided above based on trimester should only be used if your local lab company cannot calculate the TSH reference ranges for pregnant women who live local to you.

Put another way:

You should NOT be using generic reference ranges when it comes to your TSH level during pregnancy because the TSH level can vary based on geographic location, ethnicity , and other factors such as your weight and metabolism.

It’s better to CREATE reference ranges based on your location than to use the generic reference range provided above.

Unfortunately, not all lab tests do this for pregnant women because there simply isn’t enough information available.

It’s not always clear if a woman is pregnant early on which can skew the data one way or the other.

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What Happens If Hypothyroidism Is Not Treated

Hypothyroidism can become a serious and life-threatening medical condition if you do not get treatment from a healthcare provider. If you are not treated, your symptoms can become more severe and can include:

  • Developing mental health problems.
  • Not being able to maintain a normal body temperature.
  • Having heart problems.
  • Developing a goiter .

You can also develop a serious medical condition called myxedema coma. This can happen when hypothyroidism isnt treated.

Can Hypothyroidism Affect My Chances Of Getting Pregnant

The short answer is yes.

Hypothyroidism can cause irregular periods, which makes ovulation harder to track. Some women with hypothyroidism do not ovulate at all. In a study of women with infertility, 24% had hypothyroidism. After getting proper treatment for their hypothyroidism though, almost 80% of those women conceived within 6 weeks to 1 year. According to the American College of Obstetrics and Gynecology , women with infertility should have a thyroid evaluation.

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Special Considerations For Women With A History Of Graves’ Disease

In addition to the dosing and testing considerations explained in this brochure, women with a history of Graves disease who were treated with radioiodine or surgical thyroidectomy should also have Graves antibodies tested early in pregnancy to assess the risk of passing antibodies on to the fetus. If antibodies are elevated, follow-up testing is recommended at weeks 18- 22, and if antibodies are still elevated, additional follow-up is recommended at weeks 30-34 to evaluate the need for fetal and neonatal monitoring.

Treatment For Low Thyroid Levels

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  • A pregnant woman should eat food rich in iodine. Green leafy vegetables, seaweed, kelp are some of the examples of iodine rich food.
  • Eat foods high in vitamin A. carrot, green leafy vegetable, egg, fish etc are high in vitamin A. it will be beneficial for functioning of thyroid.
  • Omega -3 fatty acids containing sea food such as fish and nuts boost your metabolism and that is good for pregnant woman with low thyroid level.
  • And lastly your doctor may also prescribe medicine for better functioning of thyroid, if you suffer from low thyroid level during pregnancy.

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The Importance Of Treatment

You should begin treatment right away when you’re pregnant and you become hyperthyroid due to Graves disease or thyroid nodules. Leaving hyperthyroidism untreated can result in high blood pressure, thyroid storm, congestive heart failure, miscarriage, premature birth, low birth weight, or even stillbirth. For pregnant and non-pregnant patients, treatment typically begins with taking antithyroid medications.

In cases where you’re already being treated with a low dose of antithyroid medication and your thyroid function is normal, your doctor may take you off your medication, at least during your first trimester when your baby is most susceptible. You’ll need to be monitored closely, having your TSH and FT4 or TT4 checked every one to two weeks during the first trimester and every two to four weeks during the second and third trimesters, as long as your thyroid function remains normal.

Otherwise, if you’ve been newly diagnosed, you haven’t been taking antithyroid medication for very long, or you’re at a high risk of developing thyrotoxicosis , your dosage will likely be adjusted so that you’re on the lowest possible dose of antithyroid medication while still keeping your free T4 at the top end of the normal range or just above it. This protects your baby from overexposure since these medications are more potent for him or her than they are for you.

Do I Need To Continue To Monitor My Thyroid Levels

It is important to have blood levels checked regularly even after the correct dose is found. Hypothyroidism is often a lifelong and progressive disease and the dose of thyroid hormone replacement may need adjustment.

Frequent monitoring is important if the dose of thyroid replacement hormone is too high, women may develop treatment-induced hyperthyroidism. This could cause heart palpitations, nervousness, and osteoporosis .

If you become pregnant, your doctor will need to monitor your blood every trimester as your levothyroxine dose needs may change due to pregnancy.

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The Connection Between Hyperemesis Gravidarum And Thyroid Health

Thyroid hormone levels change during pregnancy in order to support embryo growth. But there are also differences in thyroid hormone levels between pregnant people with mild or no nausea, and those with extreme nausea.

Thyroid hormone reverse T3 is higher than usual in people with HG. This might be to help prevent weight loss caused by nausea and vomiting.

In some cases free T3 and free T4 might be higher than usual in HG patients, while TSH is slightly decreased. These changes in thyroid hormones are caused by human chorionic gonadotropin a hormone produced in early pregnancy that activates the thyroid gland in early pregnancy and can cause vomiting.

Track your thyroid hormone levelsincluding hCGin BOOST Thyroid. You can also track nausea and vomiting, as well as adjust the reference ranges for all your blood tests, in BOOST Plus.


  • Jennings LK, et al. Hyperemesis Gravidarum, 2020

  • Asakura H, et al. Severity of hyperemesis gravidarum correlates with serum levels of reverse T3, 2000

  • Juras N, et al. Increased serum reverse triiodothyronine in patients with hyperemesis gravidarum, 1983

  • Swaminathan R, et al. Thyroid function in hyperemesis gravidarum, 1989

  • Appierto U, et al. Nausea, vomiting and thyroid function before and after induced abortion in normal pregnancy, 1996

  • How Does Pregnancy Affect Thyroid Function

    Hypothyroidism and Getting Pregnant

    Thyroid hormone levels increase during pregnancy to support you and your baby. While your babys own thyroid starts working in week 10 to 12 of pregnancy, it only fully matures in the third trimester. Until then, your baby relies on your supply of thyroid hormone for their brain development.

    Good thyroid function is therefore important during pregnancy for both the mother and babys health.

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    What Causes Hypothyroidism In Pregnancy

    In most cases, women with hypothyroidism during pregnancy have Hashimotos disease. This autoimmune disease causes the bodys immune system to attack and damage the thyroid. When that happens, the thyroid cant produce and release high enough levels of thyroid hormones, impacting the entire body. Pregnant women with hypothyroidism may feel very tired, have a hard time dealing with cold temperatures and experience muscles cramps.

    Thyroid hormones are important to your babys development while in the womb. These hormones help develop the brain and nervous system. If you have hypothyroidism, its important to control your thyroid levels during pregnancy. If your baby doesnt get enough thyroid hormone during development, the brain may not develop correctly and there could be issues later. Untreated or insufficiently treated hypothyroidism during pregnancy may lead to complications like miscarriage or preterm labor.

    Talk To Your Doctor About Testing

    Women can develop hypothyroidism while theyre pregnant. Some doctors routinely check thyroid levels during pregnancy to monitor for low thyroid hormone levels. If your levels are lower than they should be, your doctor may suggest treatment.

    Some women who never had thyroid problems before they were pregnant may develop them after having a baby. This is called postpartum thyroiditis. For many women, the condition resolves within 12 to 18 months, and medication is no longer required. Approximately 20 percent of women with postpartum thyroiditis will go on to require long-term therapy.

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    What Can Cause Hypothyroidism To Appear During Pregnancy

    During pregnancy, your body uses more thyroid hormone to keep up with the needs of your growing baby. So pregnancy itself actually makes hypothyroidism more likely, and previous miscarriages or preterm deliveries may be a sign of hypothyroidism. Women who take a thyroid medication may need a new dose that is 25% to 50% higher once they become pregnant. If not, their thyroid hormone levels may drop. If you become pregnant, your provider will check your hormone levels throughout your pregnancy and make adjustments, if needed.

    • Dry skin and hair

    • Constipation

    The American College of Obstetricians and Gynecologists guidelines say providers should not routinely test for hypothyroidism in pregnant women. They only recommend testing for women who have related risk factors or symptoms. So always tell your provider how youre feeling and give them a full rundown of your medical history, including medications you take, how your previous pregnancies turned out, and if you have any family members with hypothyroidism. They will follow up and order blood tests, if necessary.

    Risks Associated With Thyroid Dysfunction In Pregnancy

    Thyroid symptoms | Thyroid during pregnancy in Tamil | Thyroid causes infertility | Thyroid types
    • Overt hypothyroidism and hyperthyroidism are associated with a range of adverse obstetric outcomes and risks to the baby .
    • Studies are now focusing on the potential effect of subclinical thyroid dysfunction and autoimmune disease. A systematic review found that subclinical hypothyroidism in pregnancy is associated with pre-eclampsia and perinatal mortality and the presence of maternal thyroid autoantibodies is associated with miscarriage and preterm birth . A meta-analysis of cohort studies had similar findings for miscarriage and another for preterm birth .

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    What Causes Hypothyroidism

    The most common cause of hypothyroidism is an autoimmune disorder called Hashimotos thyroiditis. The bodys immune system mistakenly sends out antibodies to destroy the cells in the thyroid gland. This may cause the thyroid gland to enlarge, known as goiter.

    Hypothyroidism and goiter can also result from not getting enough iodine in your diet. Hypothyroidism also can occur after thyroid surgery or radioactive iodine therapy given to treat hyperthyroidism. In many cases, the specific cause of hypothyroidism is not known.

    This Gland Is A Butterfly

    It creates and stores hormones that control the bodys heart rate , blood pressure, and metabolism .

    Low thyroid is when the thyroid gland is underactive and does not release thyroid hormones necessary for human metabolism.

    The thyroid gland normally releases necessary hormones that are transported through the bloodstream to receptors located throughout the body.

    The alteration in thyroid function causes health problems.

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    What Are The Risks During Pregnancy In Hypothyroidism

    Some potential risks with hypothyroidism are as follows: The fetus may suffer developmental delay: During the early months of pregnancy your fetus is totally Preclampsia: Hypothyroidism, if left untreated can lead to this condition. Anemia: If your metabolism system isnt working the way it should be due to lack Low Birth Weight: Your baby may be born

    Treatments For An Underactive Thyroid

    Hyperthyroidism and Getting Pregnant

    Luckily hypothyroidism is usually easy to treat. Your doctor will likely prescribe a synthetic version of the thyroid hormone. The most popular medication for this is called levothyroxine. You will need to take this medication for the rest of your life. Once you are medicated, your symptoms and complications may reduce greatly or go away completely.

    If you are taking medication for an underactive thyroid, it’s important to visit your doctor for all follow-up appointments. The amount of medication you need to take may change throughout your life. So, your doctor will check your hormone levels periodically to make sure your current dosage is correct.

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    Further Testing Is Often Necessary

    In almost every case of low TSH, you will need to get more advanced testing done.

    The TSH is the standard way physicians use to generally evaluate your thyroid, but there are many further tests that can and should be ordered.

    The TSH only gives you a specific set of information about your pituitary gland but it doesn’t give you information about the amount of circulating free thyroid hormone in your body or about how well you are converting or utilizing thyroid hormone.

    These factors can easily be evaluated by adding a few extra tests.

    Tests that you will want to get beyond the TSH include:

    • Free T3
    • Reverse T3
    • Thyroid antibodies

    These lab tests will help differentiate the various causes of low TSH and will help you have a better idea as to what is happening in your body.

    Below you will find a list of lab patterns and how they match up with the conditions listed above:

    • Low TSH, low free T3, low free T4, high reverse T3 – This pattern is seen in euthyroid sick syndrome.
    • Low TSH, very high free T3, low free T4 – This pattern is seen in cases of endogenous hyperthyroidism such as Graves’ disease.
    • Low TSH, high free T4, low free T3 – This pattern is usually seen with thyroid medication but doesn’t necessarily mean that you are hyperthyroid.
    • Low TSH, normal free T3, normal free T4 – This pattern is seen with a lab anomaly.
    • Low TSH, low free T4, low free T3, low reverse T3 – This pattern is seen in pituitary dysfunction.

    Monitor Your Soy Intake

    Soy may hinder the absorption of thyroid hormones. If you drink or eat too many soy products, you may not be able to properly absorb your medication.

    Its especially important that caregivers monitor the soy intake of infants who need hypothyroidism treatment and also drink soy formula.

    Soy is found in:

    • soybeans
    • soy sauce

    You need steady doses of the medication to achieve even levels of thyroid hormone in your blood. Avoid eating or drinking soy-based foods for at least 4 hours before and after you take your medication.

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