- Managing Pregnancy With an Underactive Thyroid
- How Hypothyroidism Affects Pregnancy
- Screening for Hypothyroidism During Pregnancy
- Hypothyroidism: Treatment During Pregnancy
- Hypothyroidism During Pregnancy: Vitamin Interactions
- This is Your Thyroid During Pregnancy
- The Risks of Thyroid Problems in Pregnancy
- Before You Conceive
- Hypothyroid, Hashimoto’s, and Miscarriage Risk
- Thyroid Function and Baby’s Well-Being
- Thyroid Medication in Pregnancy – Is it Necessary?
- To Reverse Elevated Thyroid Auto-Antibodies
- Test and Retest
- Get to the Root Causes
- The Adrenal Thyroid Revolution
- Is it safe to take thyroid medication while I’m pregnant?
- The Thyroid and Pregnancy
- Hypothyroidism and Pregnancy
- Facts about hypothyroidism and pregnancy
- What are the symptoms of hypothyroidism?
- How does hypothyroidism affect the baby in the womb?
- How is thyroid function tested?
- Who should have thyroid function testing?
- How is hypothyroidism treated during pregnancy?
- 46 Thyroid dysfunction
- 46.5 Resources
- Autism four times likelier when mother’s thyroid is weakened
- New Recommendations Call for Iodine in All Prenatal Vitamins
Managing Pregnancy With an Underactive Thyroid
Those raging pregnancy hormones that make you feel moody and have you going to sleep at 8 p.m. every night aren’t the only pregnancy hormones you should be concerned about.
When you’re pregnant, your growing baby relies on you for everything, including the hormones that your body naturally produces to keep both your bodies healthy and functioning properly. And if you have untreated hypothyroidism, or underactive thyroid, your baby might not be getting what it needs to grow and thrive during your pregnancy.
How Hypothyroidism Affects Pregnancy
Your thyroid gland produces hormones that affect your metabolism, which controls many bodily processes. Without enough of those hormones, your own body can’t function well, much less that little baby inside you.
Untreated hypothyroidism poses a number of risks for you and your developing fetus. Risks for the mother include:
- Pre-eclampsia, or pregnancy-related high blood pressure
- Weakness or muscle pain
- Vaginal bleeding after delivery
- Abnormalities in the placenta
Risks for the baby include:
- Neurological and developmental problems
- Low birth weight
While these complications can be serious, the good news is that if hypothyroidism is diagnosed and treated before you become pregnant or very early in pregnancy, they’re much less likely.
Screening for Hypothyroidism During Pregnancy
While women who have hypothyroidism before they become pregnant may have already had the opportunity to talk to their doctors about their risks and treatment options, for some women, hypothyroidism may not strike until they become pregnant.
It’s easy to develop hypothyroidism while pregnant and not know it — the symptoms can be very similar to those of pregnancy. Weight gain, swelling, and fatigue are common symptoms, but you’re probably already feeling all of those things. A blood test can diagnose hypothyroidism, but it’s up to you and your doctor to decide whether or not you should be screened.
The following could indicate the need to be screened for hypothyroidism when you become pregnant:
- A family history of thyroid conditions
- Symptoms common to an underactive thyroid, such as fatigue, constipation, feeling cold, or having dry skin and hair
Hypothyroidism: Treatment During Pregnancy
Hypothyroidism treatments are generally safe to take during pregnancy, and the same synthetic hormone (levothyroxine) given to hypothyroid patients who are not pregnant are also given during pregnancy.
An element of treatment that is likely to change during pregnancy is how much levothyroxine you need. Frequent blood tests — done every six weeks or so — are needed to determine if you’re getting the right amount of hormones. As your pregnancy progresses, you’ll likely need a higher dosage of levothyroxine; some women need as much as 50 percent more hormone medication in later stages of pregnancy. You’ll also need to continue taking your medications if you breastfeed, but probably at a lower dose. Taking thyroid hormones is perfectly safe even for breastfeeding moms; you need it to stay healthy and to produce milk for your new baby.
In 2012, The Endocrine Society made the following revisions to its clinical practice guidelines:
- Doctors should interpret serum-free thyroxine levels cautiously during pregnancy. The experts advised that using trimester-specific reference ranges would improve the interpretation of pregnant women’s thyroid-function tests.
- The drug propylthiouracil (PTU) should be the primary treatment for hyperthyroidism during the first trimester of pregnancy. The experts cautioned the alternate treatment — methimazole — may increase the risk for birth defects. Methimazole, however, can be used if PTU is unavailable or if women have a negative reaction to the drug. Because PTU may be harmful to the liver in rare cases, once women complete their first trimester, they should switch from PTU to methimazole.
- Women who are breast-feeding should take 250 micrograms of iodine daily to ensure their infants are getting 100 micrograms of iodine each day.
- Daily prenatal vitamins should contain 150 to 200 micrograms of iodine to protect women from iodine deficiency.
- Women with Graves’ disease, a history of Graves’ disease, a previous newborn with Graves’ disease or previously elevated thyroid stimulating hormone antibodies should have these antibodies measured before they are 22 weeks pregnant. These antibodies cross the placenta and can stimulate or restrict the fetal thyroid, the experts explained.
- The fetuses of women who have thyroid stimulating hormone receptor antibodies at least two to three time higher than normal or who are treated with anti-thyroid drugs should be screened for thyroid problems. This can be done during the fetal ultrasound women routinely undergo when they are between 18 and 22 weeks pregnant. An enlarged thyroid, growth restriction, severe swelling, presence of goiter, advanced bone age or heart failure could be signs of thyroid problems in a fetus.
- Fine-needle aspiration should be considered for women with nodules 5 millimeters to 1 centimeter in size who have a high-risk history or suspicious findings on an ultrasound. Women with complex nodules 1.5 centimeters to 2 centimeters also should undergo this procedure. The guidelines note that this can be delayed until after delivery for women who are at least 34 weeks pregnant.
Hypothyroidism During Pregnancy: Vitamin Interactions
One thing that pregnant women do need to know about is the potential interaction between their thyroid medication and their prenatal vitamins. These vitamins contain iron, which can affect the way that your body absorbs thyroid medication. Your prenatal vitamins are still important for the health of your pregnancy, but don’t take them at the same time that you take your thyroid medication. Try to space them out by at least two or three hours to lessen any possible interactions.
Hypothyroidism is a simple condition to manage during pregnancy, as long as you know how. So get screened if you notice unusual symptoms or have a family history of the condition, and talk to your doctor about managing treatment during pregnancy if you’ve already been diagnosed. The right dose of medication can help you have a healthy pregnancy — and a healthy baby.
Aug. 10, 2004 — High levels of thyroid hormones can have a direct toxic effect on fetal development, a new study shows. Women with thyroid problems should see their doctors — and get a blood test — right away, researchers say.
“Our data show a threefold to fourfold increase in the rate of miscarriage” in mothers with excess thyroid hormones, writes researcher Samuel Refetoff, MD, with the genetics and molecular medicine department at University of Chicago.
His paper appears in this week’s issue of the Journal of the American Medical Association (JAMA). It comes on the heels of evidence published just a few weeks ago — showing that women with thyroid deficiency should increase their dosage each week when they learn they are pregnant until tests can be done to determine their exact needs.
There’s much at stake: During those early weeks, the developing fetus is totally dependent on the mother’s supply of thyroid hormone. Too little, and the risks to the baby include impaired mental development and even death. Because the impact on babies is so serious, newborns are routinely screened for this deficiency.
A woman’s need for thyroid hormone increases during the first weeks of pregnancy; some 2% of pregnant women take supplements to prevent this deficiency.
However, the consequences of excess thyroid hormone — for the baby — are not well known. Studying this interaction has been difficult. “It’s not been clear whether the problem during pregnancy is caused by the overactivity of the mother’s body functions (because of hyperthyroidism) — or because they are giving too much hormone to the baby,” Refetoff tells WebMD. “It is impossible to dissociate one from the other.”
His study is the first to shed some light on this issue. “We’re finding that excess hormone is as bad, and probably worse, than too little,” says Refetoff. “Prescribing these hormones without testing the mother first is not wise.”
Updated January 22, 2020
After 3 miscarriages, Tara was finally able to maintain her pregnancy – only to go into labor 6 weeks early. Fortunately, her beautiful son, though premature, was healthy and didn’t need any special medical care. It was scary at first, and then got really stressful when she couldn’t, even with help from several lactation consultants, produce enough breastmilk for little Micah, who had to be given formula. She became depressed and felt like a total failure. Then she started gaining weight, rather than losing her ‘baby weight’ as she’d expected would happen. Even when Micah came home from the hospital, growing well, cooing, and happy, her depression just wouldn’t lift. Finally, at 6 months postpartum, she received a diagnosis: she had Hashimoto’s thyroiditis. Her thyroid labs had not been checked at all when she’d had the miscarriages, had not been trended during pregnancy, nor were they checked when her breastmilk production was low or to see if there was a medical reason for her depression – when she’d never struggled with depression before. While hindsight is 20/20, there’s a very good chance that many of Tara’s medical challenges – which caused her immense personal suffering – could have been prevented if these labs had been checked long ago, and her thyroid health properly cared for.
Healthy thyroid function is essential to the physical and emotional health of pregnant women and to new moms. It’s also critical for the health of the baby.
But thyroid problems often go undiagnosed during pregnancy. Studies show that when thyroid screening is done only on pregnant women who are at high risk for thyroid problems, an astonishing 55% of women with thyroid abnormalities are missed. And many of the common symptoms of hypothyroidism (when the thyroid is sluggish and underperforming) are attributed to the pregnancy itself. Those symptoms include fatigue, weight gain, GI distress, feeling depressed or anxious, and trouble sleeping. And, indeed, if you’re pregnant (even if you have the healthiest thyroid in the world) and you haven’t experienced some of those symptoms, you’re in the minority (and very lucky!) It’s easy to see how thyroid symptoms get missed during pregnancy.
Full disclosure: Thyroid problems tend to go unnoticed in non-pregnant women, too. Hypothyroidism, which predominantly affects women, is famously underdiagnosed. In fact, thyroid disease is so common among women, and so often neglected by conventional medicine, that I consider thyroid disease a feminist issue.
This is Your Thyroid During Pregnancy
During pregnancy, the body’s hormones shift as a natural response to supporting another life. Most pregnant women feel these rising hormonal tides in their day-to-day life: morning sickness, maybe some heartburn, increased appetite – all thanks to higher levels of key pregnancy-related hormones, like estrogen, progesterone, and human chorionic gonadotropin, or HCG, which is the hormone measured in blood or urine when you take a pregnancy test.
Thyroid hormone production shifts during pregnancy, too. The thyroid will produce more T4-binding globulin (TBG), which results in higher concentrations of the thyroid hormones T4 and T3 than in nonpregnant women. This helps to meet the body’s increased metabolic needs during pregnancy. (T4 and T3 are the primary hormones produced by the thyroid; if thyroid hormones are new to you and you want to learn more, click here.)
In other words, pregnancy puts increased demands on the thyroid – and that puts women who have pre-existing thyroid conditions, women who’ve had thyroid problems in previous pregnancies, and women who have subclinical hypothyroidism or nascent Hashimoto’s, at increased risk for thyroid problems during pregnancy.
The Risks of Thyroid Problems in Pregnancy
Thyroid problems in pregnancy can show up in several ways, the most common being hypothyroidism, either non-autoimmune, or autoimmune – also called Hashimoto’s.
Hypothyroidism is characterized by high TSH and low free T4. Subclinical hypothyroidism is characterized by elevated TSH but normal free T4 and T3 – or by the presence of thyroid TPO antibodies when other thyroid numbers are within the optimal range.
Overt hypothyroidism presents a greater risk of causing problems (and often more severe problems) in pregnancy, but a subclinical status should not be ignored.
The risks of hypothyroidism during pregnancy include:
- Increased rate of first-trimester miscarriage
- Preeclampsia and gestational hypertension
- Preterm delivery
- Increased rate of cesarean section
- Postpartum hemorrhage
- Impaired neurological development in children (studies have linked hypothyroidism in pregnancy to autism spectrum disorders)
Some studies have shown similar risks in pregnant women with subclinical hypothyroidism.
Further, hypothyroidism during pregnancy can be a harbinger of thyroid problems after pregnancy: the risk of developing postpartum thyroiditis increases by 40 to 60 percent if you test positive in the first or early-second trimester. And thyroid problems postpartum lead to even more fatigue than the typical exhaustion associated with being a new mom. Postpartum thyroiditis can also bring depression, hair loss, difficulty losing weight, and trouble producing adequate breast milk.
This is one of the reasons I strongly recommend simple thyroid testing early in pregnancy for all women, despite the recommendations by some professional medical organizations to only test pregnant women who are at high risk. And, if those test results show signs of thyroid problems or nascent thyroid problems, continue to get tested at regular intervals during pregnancy. Knowing about – and treating – thyroid issues early on can help prevent health risks to mother and baby during pregnancy, including one of the most heartbreaking problems associated with hypothyroidism in pregnancy: miscarriage.
Before You Conceive
Not only can thyroid problems add to postpartum exhaustion, depression, and stubborn weight loss resistance, they can also make it harder to get pregnant. Optimally, women who are trying to conceive should have their thyroid function checked and, if their labs aren’t optimal, should seek support and treatment. Women undergoing in vitro fertilization may also benefit from knowing and optimizing their thyroid numbers during the IVF process. (I’ll be writing more about thyroid health when trying to conceive in a future blog post.)
Hypothyroid, Hashimoto’s, and Miscarriage Risk
Miscarriage, although much more common than most women realize, is so often an incredibly painful experience emotionally and psychologically, and women suffer silently and all too alone. Women are generally told that ‘it just happens’ or ‘it’s for the best because there were probably chromosomal problems.’ While sometimes we just don’t know why miscarriage happens, and chromosomal problems do cause miscarriage, so can hypothyroidism – and this is a ‘fixable’ problem.
Women who test positive for TPO antibodies are at the highest risk for adverse pregnancy outcomes and miscarriage. What’s more, research suggests that these adverse outcomes occur at a lower TSH than in women without TPO antibodies. That’s why TPO antibody testing in pregnancy is SO critical – and why even if you only test positive for TPO antibodies (and all your other numbers are in range) it’s important to seek treatment.
What’s more, women who already take supplemental thyroid hormone may not be sufficiently covered by their current dose during pregnancy. Because the need for thyroid hormone in the body goes up during pregnancy, many women already taking medication may need to increase their thyroid hormone doses during the first trimester. Studies suggest that between 24 and 55 percent of women who are already on levothyroxine (a supplemental thyroid hormone medication also known as Synthroid) have elevated TSH at their first prenatal doctor’s visit.
Most labs have trimester-specific reference ranges for thyroid numbers. One large population-based study found that antibody-negative pregnant women with TSH values in the optimal range (under 2.5 mU/L) during the first trimester miscarried significantly less than antibody-negative women with TSH values between 2.5 and 5.0 in early pregnancy. Levothyroxine can be used during early gestation to help lower TSH numbers.
Low FT3 or FT4 suggest the need for further testing and possible medication to supplement thyroid hormone. Elevated anti-TPO antibodies alone in pregnancy does not suggest the need for thyroid hormone treatment, however, the supplements recommended below in this article are important for reducing these antibodies. Elevated antibodies indicate a much higher risk for progression to overt Hashimoto’s during the pregnancy, after baby is born, or later in life. Normalizing them can protect against this.
If you’re taking supplemental thyroid hormone for the first time during pregnancy, I recommend levothyroxine. Most OB’s are familiar with levothyroxine and will know how to dose and manage it for you. Many OBs are less familiar with other drugs, and because proper dosing is SO important during pregnancy, I recommend switching to a different medication only if levothyroxine doesn’t improve your lab values.
Research suggests that pregnant women who have tested positive for TPO antibodies, and who are taking levothyroxine (even when treatment duration is short), reduce the chances of pregnancy loss.
Thyroid Function and Baby’s Well-Being
Suboptimal maternal thyroid function has the potential to impact the baby’s eventual growth and development. Studies have shown that maternal hypothyroidism in early gestation is associated with poor cognitive function, poor psychomotor development, and low IQ in children. Newer research has connected maternal hypothyroidism with emotional and behavior problems in offspring. Children are also more likely to eventually experience their own thyroid problems.
Studies have linked severe hypothyroidism in early pregnancy (sometimes called maternal hypothyroxinemia) with increased risk for autism in babies. The risk for women with severe hypothyroidism of having a baby who is diagnosed with autism is 4-times greater than it is for women with optimal thyroid function. These findings add more proof to the value of testing thyroid labs early in pregnancy.
Thyroid Medication in Pregnancy – Is it Necessary?
If TSH is elevated or FT3 or FT4 are low, then taking thyroid medication is necessary. If you already have a known diagnosis of Hashimoto’s and are on medication, medication levels should automatically be adjusted with an increase of up to 50% to compensate for the additional demands of pregnancy on your metabolism and thus your thyroid. This should be done with the guidance of your midwife or doctor, and follow-up labs should be done to make sure you are at the best dose for your new prenatal needs.
To Reverse Elevated Thyroid Auto-Antibodies
Take Selenium: Selenium has been shown to reduce TPO antibodies and slow or stop the development of Hashimoto’s. Selenium is safe for pregnant women and I recommend taking up to 200 mcg/day (do not exceed that amount) during pregnancy and for up to six months after giving birth. Selenium can also be obtained from food, particularly Brazil nuts – though I recommend eating selenium-rich foods in conjunction with a supplement, not as a replacement. Just one or two Brazil nuts a day can help boost the body’s selenium stores. I also recommend other selenium-rich foods like mushrooms, chicken, eggs, lamb, cod, turkey, and halibut.
Research also suggests that taking selenium together with myo-inositol has a remarkably powerful effect on restoring TSH levels to a healthy range, reducing both TPOAb and TgAB antibodies, and enhancing thyroid hormone production. The dose is 200 mcg/day of selenium and 600 mg/day of myoinositol.
Vitamin D: Studies show that vitamin D levels tend to be lower in people with hypothyroidism. Because the body needs vitamin D to produce and use thyroid hormones, and because vitamin D is an important immune modulator that’s involved in hundreds of health-sustaining functions in the body – including bone health, mood, blood sugar regulation, and energy – it’s important to have optimal levels during pregnancy (and when not pregnant, too, for that matter!). In some cases, vitamin D is the missing link when a woman is already on supplemental thyroid hormones, but her dose needs keep changing or she’s not seeing results. Low vitamin D can be the culprit hiding in the background. Get your D tested and supplement with 2000-4000 units daily if your levels are low. Optimal blood level is between 50 and 80.
Test and Retest
If there’s one thing I hope you take away from this post, it’s the importance of testing early in pregnancy, if you’re trying to conceive, or if you’ve had a history of miscarriage or postpartum depression, and optimizing your thyroid lab numbers. The adverse outcomes associated with suboptimal thyroid function in pregnancy are real – and can be devastating – and are also preventible and reversible.
Get to the Root Causes
Here’s the good news: thyroid problems can be fixed, often with natural and lifestyle interventions. Yes, in some cases, both pregnant and nonpregnant women require supplemental thyroid hormones – and that’s not to be interpreted as a failure of lifestyle interventions – but all women with thyroid problems (whether they take thyroid medication or not) can work to heal Root Causes with natural strategies.
For more on the Root Causes of poor thyroid function and how to heal them, check out my book The Adrenal Thyroid Revolution. The strategies in the book can be especially important during pregnancy, when the thyroid is doing its work for two, and the book provides clear indications as to which supplements are – and aren’t appropriate – in pregnancy and while breastfeeding.
The Adrenal Thyroid Revolution
For more on the Root Causes of poor thyroid function and how to heal them, check out my book.
Is it safe to take thyroid medication while I’m pregnant?
Yes, it’s safe. In fact, it’s unsafe not to take thyroid medication during pregnancy if you need it. Whether you have hypothyroidism (an underactive thyroid) or the much less common hyperthyroidism (an overactive thyroid), you’ll probably need to take medication and be closely monitored.
The most common reason expecting moms take thyroid medicine is to treat hypothyroidism – when your thyroid gland doesn’t produce enough thyroid hormone. Levothyroxine, a synthetic form of thyroid hormone that’s safe for your baby, is the standard treatment. It poses no danger to your developing baby.
If you’re pregnant, you must continue to take levothyroxine and stay in close contact with your doctor. (It’s fine to take a generic brand of the medication, but this isn’t the time to switch from a generic to a brand name or vice versa. You need to stay on the same medicine during pregnancy that you were taking before.)
During pregnancy, the thyroid gland needs to produce about 40 percent more thyroid hormone for both you and your developing baby. Women who don’t receive enough thyroid hormone during pregnancy are at greater risk of complications, including miscarriage, preeclampsia, and preterm delivery. Some studies show that children whose mothers didn’t have enough thyroid hormone during pregnancy may have lower IQs.
In 2011 the American Thyroid Association published clinical guidelines written by a committee of international experts on the care of women with thyroid disease before, during, and after pregnancy. The guidelines make the following points about caring for moms-to-be who have hypothyroidism:
- Most women on levothyroxine need to increase their dose as soon as they find out that they’re pregnant. Of course, this should be done with your doctor’s help.
- The exact dose of medication needed will be based on your TSH (thyroid-stimulating hormone) level. (The goal is a TSH of less than 2.5 to 3.0 mIU/L .) Your TSH level is the best way to tell if you’re getting enough thyroid hormone. It’s measured by a simple blood test. During the first half of pregnancy, women on levothyroxine should have their TSH measured every four weeks. In the second half of pregnancy, it should be measured at least once, between 26 and 32 weeks.
After your baby arrives, your doctor will test your TSH level again, usually at six weeks. Your dose of levothyroxine will probably need to be reduced again to your pre-pregnancy level.
A rarer condition that occurs in only 0.5 percent of women is hyperthyroidism. If you have this condition, your thyroid is overactive (rather than underactive). The most common cause of hyperthyroidism is Graves’ disease, an autoimmune condition in which the body produces an antibody that causes the thyroid gland to release too much hormone.
Untreated hyperthyroidism, when severe, may adversely affect the pregnancy. However, mild levels of maternal hyperthyroidism are often safe.
Women with moderate to severe Graves’ disease may therefore need to receive appropriate treatment. Two antithyroid drugs – propylthiouracil and methimazole – are the mainstay of treatment of Graves’ disease during pregnancy. These drugs work to reduce the amount of hormone that the thyroid gland releases.
Unfortunately, both propylthiouracil and methimazole have been associated with rare birth defects. The type and severity of birth defects may be worse with methimazole, but both medications should be avoided (especially in early pregnancy) unless required.
Nonetheless, there are times when such medications are necessary and can help reduce medical complications. Your thyroid physician can help make the best decision about the use of these medications.
In general, when they’re needed, your doctor will give you the least amount of drug necessary to achieve control of your thyroid hormones.
The care of a pregnant woman with Graves’ disease is complicated. For one thing, the dose of the medicine needed diminishes as the pregnancy progresses. In fact, many (but not all) women are taken off all antithyroid drugs before delivery.
In addition, both of these antithyroid drugs cross the placenta and can affect the developing baby. To complicate matters even further, the antibody that causes Graves’ disease also (rarely) crosses the placenta and can affect the baby. Even women who have been successfully treated for Graves’ disease may still have this antibody and require special monitoring during pregnancy.
After your baby arrives, your doctor will continue to monitor you to make sure your medication is adjusted correctly. It’s not uncommon for Graves’ disease to flare up in the postpartum period.
Your baby’s doctor will also monitor your newborn for thyroid problems that may be present at birth. This is a rare occurrence, but your doctor has to watch out for it.
Learn how thyroid problems can affect you if you’re trying to get pregnant.
The Thyroid and Pregnancy
Even before conception, thyroid conditions that have lingered untreated can hinder a woman’s ability to become pregnant or can lead to miscarriage. Fortunately, most thyroid problems that affect pregnancy are easily treated. The difficulty lies in recognizing a thyroid problem during a time when some of the chief complaints — fatigue, constipation and heat intolerance — can be either the normal side effects of pregnancy or signals that something is wrong with the thyroid.
Although detecting a thyroid problem is important, it is equally necessary for those already diagnosed with a condition to have the thyroid checked if they are planning to become pregnant or are pregnant. Thyroid hormone is necessary for normal brain development. In early pregnancy, babies get thyroid hormone from their mothers. Later on, as the baby’s thyroid develops, it makes its own thyroid hormone. An adequate amount of iodine is needed to produce fetal and maternal thyroid hormone. The best way to ensure adequate amounts of iodine reach the unborn child is for the mother to take a prenatal vitamin with a sufficient amount of iodine. Not all prenatal vitamins contain iodine, so be sure to check labels properly.
Thyroid Disorders and Miscarriage
A woman with untreated hypothyroidism is at the greatest risk for a miscarriage during her first trimester. Unless the case is mild, women with untreated hyperthyroidism are also at risk for miscarriage.
Who should be tested?
Despite the impact thyroid diseases can have on a mother and baby, whether to test every pregnant woman remains controversial. As it stands, doctors recommend that all women at high risk for thyroid disease or women who are experiencing symptoms should have a TSH and an estimate of free thyroxine blood tests and other thyroid blood tests, if warranted. A woman is at a high risk if she has a history of thyroid disease or thyroid autoimmunity, a family history of thyroid disease, type 1 diabetes mellitus or any other autoimmune condition. Anyone with these risk factors should be sure to tell their obstetrician or family physician. Ideally, women should be tested prior to becoming pregnant at prenatal counseling and as soon as they know they are pregnant.
Hypothyroidism & Pregnancy
When a woman is pregnant, her body needs enough thyroid hormone to support a developing fetus and her own expanded metabolic needs. Healthy thyroid glands naturally meet increased thyroid hormone requirements. If someone has Hashimoto’s thyroiditis or an already overtaxed thyroid gland, thyroid hormone levels may decline further. So, women with an undetected mild thyroid problem may suddenly find themselves with pronounced symptoms of hypothyroidism after becoming pregnant.
Most women who develop hypothyroidism during pregnancy have mild disease and may experience only mild symptoms or sometimes no symptoms. However, having a mild, undiagnosed condition before becoming pregnant may worsen a woman’s condition. A range of signs and symptoms may be experienced, but it is important to be aware that these can be easily written off as normal features of pregnancy. Untreated hypothyroidism, even a mild version, may contribute to pregnancy complications. Treatment with sufficient amounts of thyroid hormone replacement significantly reduces the risk for developing pregnancy complications associated with hypothyroidism, such as premature birth, preeclampsia, miscarriage, postpartum hemorrhage, anemia and abruptio placentae.
For a woman being treated for hypothyroidism, it’s imperative to have her thyroid checked as soon as the pregnancy is detected so that medication levels may be adjusted. TSH levels may be checked one to two weeks after the initial dose adjustment to be sure it’s normalizing. Once the TSH levels drop, less frequent check-ups are necessary during the pregnancy. Although thyroid hormone requirements are likely to increase throughout the pregnancy, they tend to eventually stabilize by the middle of pregnancy. The goal is to keep TSH levels within normal ranges, which are somewhat different than proper levels in a non-pregnant woman. Pre-pregnancy doses are usually resumed after giving birth.
There is no difference between treating hypothyroidism when a woman is pregnant than when she isn’t. Levothyroxine sodium pills are completely safe for use during pregnancy. They will be prescribed in dosages that are aimed at replacing the thyroid hormone the thyroid isn’t making so that the TSH level is kept within normal ranges. Once it is consistently in the normal range, the doctor will check TSH levels every six weeks or so. The physician may also counsel patients to take their thyroid hormone pills at least one-half hour to one hour before or at least four hours after eating or taking iron-containing prenatal vitamins and calcium supplements, which can interfere with the absorption of thyroid hormone.
Hyperthyroidism & Pregnancy
Diagnosing hyperthyroidism based on symptoms can be tricky because pregnancy and hyperthyroidism share a host of features. Still, one should be aware of the symptoms and bring them to the attention of a doctor if they are experiencing them. For instance, feeling a heart flutter or suddenly becoming short of breath, both symptoms of hyperthyroidism, can be normal in pregnancy, but a doctor still may want to investigate these symptoms. An individual with any risk factors for thyroid disease should make certain they are tested.
Very mild hyperthyroidism usually does not require treatment, only routine monitoring with blood tests to make sure the disease does not progress. More serious conditions require treatment. However, treatment options are limited for pregnant women. Radioactive iodine, which is typically used to treat Graves’ disease, cannot be used during pregnancy because it easily crosses the placenta, potentially damaging the baby’s thyroid gland and causing hypothyroidism in the baby.
Due to its potential risks, the goal of treatment is to use the minimal amount of antithyroid drugs possible to maintain a patient’s T4 and T3 levels at or just above the upper level of normal, while keeping TSH levels low. When hormones reach the desired levels, drug doses can be reduced. This approach controls hyperthyroidism while minimizing the changes of a baby developing hypothyroidism.
Hyperthyroidism, if untreated, can lead to stillbirth, premature birth, or low birth weight for the baby. Sometimes it leads to fetal tachycardia, which is an abnormally fast pulse in the fetus. Women with Graves’ disease have antibodies that stimulate their thyroid gland. These antibodies can cross the placenta and stimulate a baby’s thyroid gland. If antibody levels are high enough, the baby could develop fetal hyperthyroidism, or neonatal hyperthyroidism.
A woman with hyperthyroidism while pregnant is at an increased risk for experiencing any of the signs and symptoms of hyperthyroidism. And unless the condition is mild, if it is not treated promptly a woman could miscarry during the first trimester; develop congestive heart failure, preeclampsia, or anemia; and, rarely, develop a severe form of hyperthyroidism called thyroid storm, which can be life threatening.
Graves’ disease tends to strike women during their reproductive years, so it should come as no surprise that it occasionally occurs in pregnant women. Pregnancy may worsen a preexisting case of Graves’ disease. Graves’ disease can also emerge for the first time, typically during the first trimester of pregnancy. The disease is usually at its worst during the first trimester. It tends to then improve in the second and third trimesters and flare up again after delivery.
Hypothyroidism and Pregnancy
Facts about hypothyroidism and pregnancy
Hypothyroidism is a condition that is caused by an underactive thyroid gland. It may happen during pregnancy. Many symptoms of the condition are similar to pregnancy symptoms. For example, they can both cause fatigue, weight gain, and changes in menstruation. Having low thyroid hormone levels can also cause problems with becoming pregnant. It can also be a cause of miscarriage.
What are the symptoms of hypothyroidism?
Hypothyroidism is a common condition. It can go undetected if symptoms are mild. The thyroid doesn’t make enough thyroid hormones. Symptoms may be mild and may start slowly. The most common symptoms include:
Inability to stand cold temperatures
Swelling of the face
Skin and hair changes, including dry skin and loss of eyebrows
Carpal tunnel syndrome (hand tingling or pain)
Slow heart rate
Shortness of breath with activity
Muscle cramps, weakness, joint pain
Irregular menstrual periods
The symptoms may be like other health problems. Talk with your healthcare provider for a diagnosis.
How does hypothyroidism affect the baby in the womb?
During the first few months of pregnancy, the baby relies on the mother for thyroid hormones. These hormones are vital for normal brain development and growth of the baby. Hypothyroidism in the mother can have long-lasting effects on the baby.
How is thyroid function tested?
You will have blood tests that measure thyroid hormone (thyroxine, or T4) and serum TSH (thyroid-stimulating hormone) levels. TSH levels that are above normal and T4 levels that are below normal may mean you have hypothyroidism.
Who should have thyroid function testing?
Routine screening for hypothyroidism during pregnancy is not advised. A pregnant woman with symptoms of hypothyroidism, a history of the condition, or with other endocrine system conditions should be tested.
How is hypothyroidism treated during pregnancy?
Thyroid hormone replacement is used to treat the mother. The amount of thyroid hormone given is based on the mother’s levels of thyroid hormones as well as her symptoms. Thyroid hormone levels may change during pregnancy. The hormone replacement dose will likely change over time. Thyroid hormone levels need to be checked every 4 weeks in the first half of pregnancy. The levels may be checked less often during the second half of pregnancy as long as the dose does not change. The treatment is safe and vital to both mother and baby. Thyroid hormones should not be taken at the same time as prenatal vitamins. This is because the minerals in the vitamins may stop the absorption of the thyroid hormone. All newborns are screened at birth to check thyroid hormone levels.
WEDNESDAY, Jan. 25, 2017 (HealthDay News) — Many women may be affected by an underactive thyroid gland, but new research suggests that treating it in pregnancy comes with benefits and potential harm.
“Our findings lead us to believe that overtreatment could be possible,” study co-author and Mayo Clinic endocrinologist Juan Brito Campana said in a Mayo news release.
Campana and his colleagues advise a more nuanced approach when deciding whether or not to treat a pregnant woman for a mildly underactive thyroid.
The thyroid is a butterfly-shaped gland in the neck that produces hormones vital to metabolism, growth and maturation. But the gland can produce too much hormone (hyperthyroidism) or two little (hypothyroidism), according to the U.S. National Institutes of Health.
A mildly underactive thyroid gland — “subclinical hypothyroidism” — causes a slight rise in levels of thyroid stimulating hormone (TSH) in the bloodstream, the Mayo researchers explained. This condition is estimated to occur in about 15 percent of pregnancies in the United States.
Doctors have long known that hormonal treatment for a mildly underactive thyroid can reduce the risk of pregnancy loss.
“A recent analysis of 18 studies showed that pregnant women with untreated subclinical hypothyroidism are at higher risk for pregnancy loss, placental abruption, premature rupture of membranes, and neonatal death,” said Dr. Spyridoula Maraka. She is a Mayo endocrinologist and lead author of the study.
“It seemed likely that treating subclinical hypothyroidism would reduce the chance of these deadly occurrences,” she said in the news release. “But we know that treatment brings other risks, so we wanted to find the point at which benefits outweighed risks.”
Current guidelines recommend thyroid hormone treatment for pregnant women with subclinical hypothyroidism, the Mayo team noted.
But could treatment have its own downside? To find out, Maraka’s team tracked data from more than 5,400 pregnant women with subclinical hypothyroidism.
The researchers found that only 16 percent received thyroid hormone treatment. And, as expected, women who received treatment had a lower risk of pregnancy loss.
However, these women also had higher rates of preterm delivery, gestational diabetes, and preeclampsia (a dangerous spike in blood pressure during pregnancy), the findings showed.
46 Thyroid dysfunction
- Discuss the reasons for thyroid function testing
Explain that it is important to check a woman’s thyroid hormone levels because of the effects that thyroid problems can have on the pregnancy and the baby.
- Use pregnancy specific ranges
If interpreting thyroid function test results, use pregnancy-specific reference ranges appropriate to the method used by the laboratory, that take into consideration gestational age and fetal number.
- Take a holistic approach
While iodine fortification of bread in Australia means that women will likely enter pregnancy with adequate iodine intake, supplementation (150 micrograms a day) is still recommended during pregnancy and breastfeeding. Women who have recently arrived in Australia may have previous exposure to inadequate or excessive iodine, depending on their country of origin.
- Document and follow-up
If a woman’s thyroid function is tested, tell her the results and note them in her antenatal record. Also, note whether thyroid dysfunction is newly diagnosed or was previously treated. Have a follow-up system in place to facilitate timely referral and treatment.
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- NICE (updated 2016) Antenatal Care for Uncomplicated Pregnancies CG62. London: National Institute for Health and Care Excellence.
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Last updated: 29 May 2019 Tags:
Autism four times likelier when mother’s thyroid is weakened
The association emerged from a study of more than 4,000 Dutch mothers and their children, and it supports a growing view that autism spectrum disorders can be caused by a lack of maternal thyroid hormone, which past studies have shown is crucial to the migration of fetal brain cells during embryo development.
“It is increasingly apparent to us that autism is caused by environmental factors in most cases, not by genetics,” said lead author Gustavo Román, M.D., a neurologist and neuroepidemiologist who directs the Nantz National Alzheimer Center. “That gives me hope that prevention is possible.”
The researchers also found that autistic children had more pronounced symptoms if their mothers were severely deficient for T4, also called thyroxine. Mild T4 deficiencies in mothers produced an insignificant increase in autistic children’s symptoms.
The most common cause of thyroid hormone deficiency is a lack of dietary iodine — because both the thyroid hormones, T3 and T4, contain that element.
Iodine deficiency is common throughout the world, including developed countries. The World Health Organization estimates nearly 1 in 3 people are affected globally. A 2005 CDC-University of Kansas study estimated that in the U.S., where iodine deficiency had been practically eradicated thanks to iodized salt, 1 in 7 Americans is believed deficient.
The present work was based on the Generation R Study, conducted by Erasmus Medical Centre (Rotterdam, Netherlands) doctors and social scientists, in which thousands of pregnant women were voluntarily enrolled between 2002 and 2006.
Blood was withdrawn from the mothers at or around 13 weeks into their pregnancies to measure levels of T4 and two proteins that could indicate the cause of thyroid deficiency. Six years later, mothers were asked to describe the behavioral and emotional characteristics of their children using a standardized psychology checklist.
Researchers identified 80 “probable autistic children” from a population of 4,039 — a number consistent with the Dutch rate of autism spectrum disorders. 159 mothers were identified as being severely T4 deficient (defined as having 5 percent or less of normal T4, but producing a normal amount of thyroid stimulating hormone), and 136 were identified as mildly T4 deficient. The researchers found a weak association between mild T4 deficiency and the likelihood of producing an autistic child, but a strong association between severe T4 deficiency and autism (3.89 more likely, as compared with mothers with normal thyroid hormone).
Román, who is a physician, says he has advice for women who are now pregnant, or who are considering having children. “If you are planning to become pregnant, have your doctor measure urine iodine and thyroid function beforehand. If you have just become pregnant, have your doctor measure urine iodine, thyroid function, and begin using prenatal vitamins, making sure iodine is present.”
A lack of dietary iodine interferes with normal thyroid function, leading to pregnancy complications, as well as deafness and developmental delay in the baby and loss of control of fat and sugar metabolism and heat generation in the mother.
It is well established that expecting mothers’ poor thyroid function (whether caused by poor diet, disease, or genetics) can lead to serious problems with fetal brain development, but only in the last 10 years or so has hypothyroidism been implicated as a possible cause of autism spectrum disorders.
Previous work by Román and others has shown that a deficiency of T4 during a crucial period of embryonic development causes mild to severe brain development errors, such as the lackluster migration of specialized brain cells from the cortex to the outer areas of the cerebrum — a characteristic of autistic brains. In a 2007 review Román published in the Journal of the Neurological Sciences, he presented a wide swath of evidence that the near-epidemic rise in autism diagnoses — which Román says cannot be accounted for by heightened awareness alone — could be at least partly the result of an iodine-starved diet and/or exposure to toxins that interfere with normal thyroid function.
The Annals of Neurology study presents a troubling correlation, but it does not prove that the thyroid function of expecting mothers causes autism in their children.
“The next steps are interventional studies,” Román said. “We must look at a large nationwide population of women in early pregnancy, to measure urine iodine and thyroid function. We must then correct thyroid deficiencies, if present, and provide prenatal vitamins with supplementary iodine. If autism cases fall precipitously compared with recent historical numbers, I think we will be able to conclude that thyroid function is critical.”
New Recommendations Call for Iodine in All Prenatal Vitamins
Endocrinology groups are applauding a new recommendation from a dietary-supplement trade association that calls for iodine supplementation in all prenatal vitamins prescribed for pregnant and breastfeeding women.
In addition, the public health committee of the American Thyroid Association (ATA) recently published a statement reiterating the ATA recommendation that women take a daily multivitamin containing 150 μg of iodine during prepregnancy, pregnancy, and lactation. The statement also warns of the potential risks of excess iodine consumption and exposure, particularly through the use of unregulated kelp supplements.
The US Council for Responsible Nutrition’s new guidelines call for all dietary-supplement manufacturers and marketers to begin including at least 150 μg of iodine in all daily multivitamin/mineral supplements intended for pregnant and lactating women in the United States within the next 12 months.
The ATA had lobbied for the move, in conjunction with the Endocrine Society, the American Association of Clinical Endocrinologists, the Iodine Global Network, and the Teratology Society.
“A number of organizations have been trying to get iodine in prenatal vitamins,” endocrinologist Alex Stagnaro-Green, MD, from the University of Illinois College of Medicine, Rockford, and chair of the ATA task force on thyroid disease during pregnancy and postpartum, told Medscape Medical News. “This is a huge win for public health, from my perspective and the perspective of the ATA.”
In the past several years, removal of iodized salt from commercial products such as bread and milk, along with increased use of kosher salt and sea salt, which don’t contain iodine, and the adoption of vegetarian and vegan diets have led to a reduction in dietary iodine consumption. “There never was a coherent US policy about iodization,” Dr Stagnaro-Green noted.
Worldwide, about two billion people are iodine-deficient. While most of the US population has adequate iodine levels, data from the National Health and Nutrition Examination Survey suggest that more than half of pregnant women have urinary iodine concentrations below 150 mg/dL (Thyroid. 2011;21:419-427).
Pregnant women actually need more iodine than other people because of increased thyroid-hormone production, renal losses, and fetal iodine requirements. Iodine deficiency during pregnancy can result in maternal and fetal goiter, cretinism, intellectual impairment, neonatal hypothyroidism, and increased pregnancy loss and mortality, Dr Stagnaro-Green and colleagues explained in a 2012 editorial (JAMA 2012;308:2463-2464).
“So, women of childbearing age are the subpopulation of Americans with the lowest iodine levels yet have the greatest need during pregnancy and breastfeeding, for the neurodevelopment of the fetal and neonatal brain,” he told Medscape Medical News.
In 2009, a study found that only 51% of US prenatal multivitamin brands contained any iodine and, in a number of randomly selected brands, the actual dose of iodine contained in the supplements did not match values on the labeling.
When asked about this new recommendation from the trade association, Dr Stagnaro-Green said, “I would classify it as a triumph.”
Now, the ATA and the other groups are lobbying for placement of the iodine prenatal vitamin supplement recommendation into the upcoming Dietary Guidelines for Americans.
However, the American College of Obstetricians and Gynecologists (ACOG) has not joined in these efforts. While the group does recommend the 150-μg dose for pregnant and lactating women, it does not currently endorse the prenatal-supplement recommendation, advising instead that women get their iodine through dietary sources.
Scott Sullivan, MD, from the Medical University of South Carolina, Charleston, who has worked with ACOG on this issue, told Medscape Medical News , “Prenatal iodine supplementation has been under discussion at ACOG and for some time. No one questions the fact that American women have a risk for iodine deficiency, some in the severe range. What is lacking is a randomized controlled trial that demonstrates improved maternal, fetal, or neonatal outcome with universal iodine supplementation. ACOG usually will not endorse a recommendation until those data are available.”
However, he added, “I personally have been a signatory to both the Endocrine Society and the American Thyroid Association guidelines, which both recommend universal iodine supplementation, ideally through prenatal vitamins, in pregnancy. I do this with my personal patients and recommend it when consulted. I believe that as data continue to come in, this will be proven to be a winning strategy for pregnant women.”
But Don’t Overdo It
In the ATA’s public health committee statement, Angela M Leung, MD, from the University of California Los Angeles David Geffen School of Medicine, and colleagues, including Dr Stagnaro-Green, note that iodine is a micronutrient required for normal thyroid function. The US recommended daily allowances (RDA) for iodine intake are 150 μg in adults, 220 to 250 μg in pregnant women, and 250 to 290 μg in breastfeeding women. Dietary sources such as iodized salt, dairy products, some breads, and seafood usually contain enough to meet the RDA for most people who aren’t pregnant or lactating.
However, there is an upper safety limit, with ingestion of more than 1100 μg/day not recommended due to the risk for thyroid dysfunction. In particular, infants, the elderly, pregnant and lactating women, and people with preexisting thyroid disease are at risk for adverse effects of excess iodine on the thyroid.
Many iodine, potassium iodide, and kelp supplements contain hundredfold greater amounts of iodine than the recommended upper limit, Dr Leung and colleagues caution.
“Given the increasing popularity of iodine and kelp supplements, recommendations cautioning against excess iodine were indicated. The potential result of iodine-induced thyroid dysfunction, which may be particularly harmful during pregnancy and breastfeeding and in the elderly, may not be well-known,” she told Medscape Medical News.
There are a few specific clinical scenarios in which the short-term use of high-dose iodine is indicated, such as for the treatment of thyroid storm, prior to surgery for Graves’ disease, for individuals living in the vicinity of a nuclear power plant to be used in the event of an accident, and for patients who need to receive iodinated contrast dyes for radiologic studies.
In such instances, patients should be monitored for iodine-induced thyroid dysfunction, Dr Leung and colleagues advise.
Referring to both of the ATA recent statements, she told Medscape Medical News, “We hope that these two recent articles highlight the critical importance of the appropriate amount of iodine intake, particularly among pregnant and breastfeeding women in whom there may be adverse effects to the developing fetus and newborn infant with both iodine deficiency and iodine excess.”
Dr Leung and colleagues report no relevant financial relationships, as do Dr Stagnaro-Green and Dr Sullivan.
Thyroid. 2015;25:145-146. Abstract