Continued national iodine monitoring is needed with more emphasis on population subgroups that are most susceptible to iodine deficiency disorders. Iodine deficiency has multiple adverse effects on growth and development and is the most common cause of preventable intellectual disability in the world [ 41 ].

Iodine deficiency disorders result from inadequate thyroid hormone production secondary to insufficient iodine [ 5 ]. During pregnancy and early infancy, iodine deficiency can cause irreversible effects. Under normal conditions, the body tightly controls thyroid hormone concentrations via TSH.

TSH increases thyroidal iodine uptake from the blood and the production of thyroid hormone. However, very low iodine intakes can reduce thyroid hormone production even in the presence of elevated TSH levels.

Goiter is usually the earliest clinical sign of iodine deficiency [ 2 ]. In pregnant women, iodine deficiency of this magnitude can cause major neurodevelopmental deficits and growth retardation in the fetus as well as miscarriage and stillbirth [ 5 ].

Chronic, severe iodine deficiency in utero causes cretinism, a condition characterized by intellectual disability, deaf mutism, motor spasticity, stunted growth, delayed sexual maturation, and other physical and neurological abnormalities [ 5 ].

In infants and children, less severe iodine deficiency can also cause neurodevelopmental deficits such as somewhat lower than average intelligence as measured by IQ [ 1 , 42 , 43 ]. Mild to moderate maternal iodine deficiency has also been associated with an increased risk of attention deficit hyperactivity disorder in children [ 44 ].

In adults, mild to moderate iodine deficiency can cause goiter as well as impaired mental function and work productivity secondary to hypothyroidism.

Chronic iodine deficiency may be associated with an increased risk of the follicular form of thyroid cancer [ 45 ]. Historically, iodine deficiency was endemic in mountainous regions of the United States and Mexico, and in the so called goiter belt around the Great Lakes [ 46 ].

Thanks to a more national food supply, iodized salt, and other factors, overt iodine deficiency is now uncommon in North America.

International efforts since the early s have dramatically reduced the incidence of iodine deficiency worldwide, but some groups of people are still at risk of inadequate iodine intake. Iodine insufficiency remains a public health problem in 25 countries with a total population of about million people [ 47 ].

The following groups are among those most likely to have inadequate iodine status. The use of iodized salt is the most widely used strategy to control iodine deficiency.

Surveys indicate that many pregnant women in the United States might consume insufficient amounts of iodine even if they do not have signs or symptoms of overt iodine deficiency [ 36 ]. The impact, if any, of this insufficient intake on fetal development is not known.

Seafood, eggs, milk, and milk products are among the best sources of iodine. Vegans, people with certain food allergies or lactose intolerance, and others who consume no or minimal amounts of these foods might not obtain sufficient amounts of iodine [ 49 , 50 ].

Iodine-deficient soils produce crops that have low iodine levels. Mountainous areas e. People living in these areas are at risk of iodine deficiency unless they consume iodized salt or foods produced outside the iodine-deficient area. Consumption of foods that contain goitrogens, substances that interfere with the uptake of iodine in the thyroid, can exacerbate iodine deficiency [ 2 ].

Foods high in goitrogens include soy, cassava, and cruciferous vegetables e. These issues are of concern primarily for people living in areas prone to iodine deficiency [ 6 ]. For most people, including most of the U. population, who have adequate iodine intakes and eat a variety of foods, the consumption of reasonable amounts of foods containing goitrogens is not a concern.

Due to its important role in fetal and infant development and thyroid hormone production, iodine is a critical nutrient for proper health at all life stages. Iodine sufficiency during pregnancy is extremely important for proper fetal development.

During early pregnancy, when fetal thyroid gland development is incomplete, the fetus depends entirely on maternal T4 and, therefore, on maternal iodine intake [ 52 ].

Sufficient iodine intake after birth is also important for proper physical and neurological growth and maturation. Research suggests that infants are more sensitive to the effects of iodine deficiency than other age groups, as indicated by changes in their TSH and T4 levels in response to even mild iodine deficiency [ 54 ].

Although severe iodine deficiency disorders are uncommon in the United States, mild to moderate iodine insufficiency during pregnancy may subtly affect fetal development [ 4 , ].

A meta-analysis of 6, mother-child pairs from three birth cohorts in the Netherlands, Spain, and the United Kingdom found that verbal IQ assessed in children at 1. Despite the importance of iodine for proper fetal development, the effects of iodine supplements during pregnancy on infant and child neurodevelopment in particular are inconclusive.

Iodine supplementation had no effect on child cognitive, language, or motor scores [ 62 ]. Breast milk contains iodine, although concentrations vary based on maternal iodine levels.

Infants who are exclusively breastfed depend on maternal iodine sufficiency for optimal development. During the weaning period, infants not receiving iodine-containing complementary foods may also be at risk of iodine deficiency, even in countries with iodized salt programs [ 64 , 65 ].

To ensure that adequate amounts of iodine are available for proper fetal and infant development, several national and international groups recommend iodine supplementation during pregnancy, lactation, and early childhood.

WHO recommendations for these countries also include breastfeeding through 24 months of age, combined with complementary foods fortified with iodine for children between the ages of 7—24 months [ 7 ]. Similarly, the American Academy of Pediatrics recommends that women who are pregnant, planning to become pregnant, or lactating take a daily supplement providing at least mcg iodine and use iodized salt [ 67 ].

The use of iodine-containing dietary supplements by pregnant and lactating women in the United States appears to be low compared to current recommendations. Of 59 best-selling prenatal multivitamin supplements on the market in —, only 34 contained iodine [ 22 ].

The median iodine content was mcg per daily serving, with a range of 25 to mcg; 25 of the 34 provided iodine as potassium iodide. According to — NHANES data, Results from a study, however, raise some questions as to the safety of widespread iodine supplementation in areas of relative iodine sufficiency.

These findings suggest that taking higher doses of supplemental iodine during pregnancy could induce thyroid dysfunction in some women and underscore the need for additional research into the effects on maternal thyroid function of iodine supplementation during pregnancy.

Many researchers, as well as the American Thyroid Association, stress the importance of continued iodine status monitoring among women of reproductive age [ 1 , 4 , 32 , 38 , 56 , 70 , 71 ].

The effects of severe iodine deficiency on neurological development are well documented. Results from several studies suggest, for example, that chronic, moderate to severe iodine deficiency, particularly in children, reduces IQ by about 12— A Cochrane Review concluded that iodine supplementation in children living in areas of iodine deficiency appears to both positively affect physical and mental development and decrease mortality with only minor and transient adverse effects [ 72 ].

The effects of mild iodine deficiency during childhood are more difficult to quantify. Some research suggests that mild iodine deficiency is associated with subtle neurodevelopmental deficits and that iodine supplementation might improve cognitive function in mildly iodine-deficient children [ 52 ].

These findings suggest that correcting mild iodine deficiency in children could improve certain components of cognition. Additional research is required to fully understand the effects of mild iodine deficiency and iodine supplementation on cognitive function.

Fibrocystic breast disease is a benign condition characterized by lumpy, painful breasts and palpable fibrosis.

It commonly affects women of reproductive age, but it can also occur during menopause, especially in women taking estrogens [ 74 ]. Breast tissue has a high concentration of iodine, especially during pregnancy and lactation [ 4 , 75 ].

Some research suggests that iodine supplementation might be helpful for fibrocystic breast disease, although a specific mechanism of action has not been established [ 76 ] and data are limited. A more recent randomized, double-blind, placebo-controlled clinical trial had similar findings.

In this study, researchers randomly assigned women 18—50 years of age with fibrosis and a history of breast pain to receive tablets containing 0 mcg, 1, mcg, 3, mcg, or 6, mcg of iodine per day [ 76 ]. After 5 months of treatment, women receiving doses of 3, or 6, mcg iodine had a significant decrease in breast pain, tenderness, and nodularity compared with those receiving placebo or 1, mcg iodine.

The researchers also reported a dose-dependent reduction in self-assessed pain. None of the doses was associated with major adverse events or changes in thyroid function test results.

Moreover, the doses used in these studies approximately 1,—6, mcg per day are several times higher than the iodine UL of 1, mcg for adults. Doses of this magnitude should only be used under the guidance of a physician [ 2 ]. Nuclear accidents can release radioactive iodine into the environment, increasing the risk of thyroid cancer in exposed individuals, especially children [ 77 , 78 ].

Thyroidal uptake of radioactive iodine is higher in people with iodine deficiency than in people with iodine sufficiency. For this reason, iodine-deficient individuals have a particularly high risk of developing radiation-induced thyroid cancer when exposed to radioactive iodine.

FDA has approved potassium iodide as a thyroid-blocking agent to reduce the risk of thyroid cancer in radiation emergencies involving the release of radioactive iodine [ 77 ]. FDA recommends that exposed people take a daily pharmacological dose 16— mg potassium iodide, depending on age until the risk of significant radiation exposure ends [ 77 , 78 ].

Potassium iodide was widely used in Poland following the Chernobyl accident and childhood thyroid cancer rates did not increase substantially in subsequent years [ 79 ]. In areas where iodide prophylaxis was not used, such as Belarus and Ukraine, where many children were mildly iodine deficient, the incidence of thyroid cancer sharply increased among children and adolescents [ 77 ].

High intakes of iodine can cause some of the same symptoms as iodine deficiency—including goiter, elevated TSH levels, and hypothyroidism—because excess iodine in susceptible individuals inhibits thyroid hormone synthesis and thereby increases TSH stimulation, which can produce goiter [ 2 , 80 ].

Iodine-induced hyperthyroidism can also result from high iodine intakes, including when iodine is administered to treat iodine deficiency. Studies have also shown that excessive iodine intakes cause thyroiditis and thyroid papillary cancer [ 2 , 80 ].

Cases of acute iodine poisoning are rare and are usually caused by doses of many grams. Acute poisoning symptoms include burning of the mouth, throat, and stomach; fever; abdominal pain; nausea; vomiting; diarrhea; weak pulse; and coma [ 2 ].

Responses to excess iodine and the doses required to cause adverse effects vary [ 81 ]. Some people, such as those with autoimmune thyroid disease and iodine deficiency, may experience adverse effects with iodine intakes considered safe for the general population [ 2 , 5 ].

The FNB has established iodine ULs for food and supplement intakes Table 3. In most people, iodine intakes from foods and supplements are unlikely to exceed the UL [ 2 ].

Long-term intakes above the UL increase the risk of adverse health effects. The ULs do not apply to individuals receiving iodine for medical treatment, but such individuals should be under the care of a physician [ 2 ].

Iodine supplements have the potential to interact with several types of medications. A few examples are provided below. Individuals taking these medications on a regular basis should discuss their iodine intakes with their health care providers. Antithyroid medications, such as methimazole Tapazole , are used to treat hyperthyroidism.

Taking high doses of iodine with antithyroid medications can have an additive effect [ 81 ] and could cause hypothyroidism. Angiotensin-converting enzyme ACE inhibitors, such as benazepril Lotensin , lisinopril Prinivil and Zestril , and fosinopril Monopril , are used primarily to treat high blood pressure.

Taking potassium iodide with ACE inhibitors can increase the risk of hyperkalemia elevated blood levels of potassium [ 81 ]. Among them:. Many types of treatment comprise traditional Chinese medicine, so if you decide to explore TCM as a complement to the conventional therapies you may be receiving for thyroid disease, don't be surprised if the practitioner devises an approach that's very different from those described here.

That's largely because of the highly individualized approach to diagnosing and treating disease that's the linchpin of TCM. The one thing all people who turn to Chinese medicine for treatment of thyroid disease should share, however, is maintaining an open and honest dialogue with their primary caregiver to make certain that any non-traditional treatments they may want to try won't interfere with any conventional medicines or therapies they may be receiving.

Malikov D. Traditional chinese medicine approach to hypothyroidism. Int J Complement Alt Med. National Center for Complementary and Integrative Health. Traditional chinese medicine: what you need to know. Pacific College of Oriental Medicine.

Traditional chinese medicine and thyroid disease. Cheng FK. An overview of the contribution of acupuncture to thyroid disorders. J Integr Med. British Acupuncture Council. Thyroid disease.

Yi YD, Chang IM. An overview of traditional chinese herbal formulae and a proposal of a new code system for expressing the formula titles.

Evid Based Complement Alternat Med. Zhang Y, Li Y, Mao X, et al. Thyroid hormone synthesis: a potential target of a Chinese herbal formula Haizao Yuhu Decoction acting on iodine-deficient goiter. Yang ML, Lu B. Treatment of goiter with traditional chinese medicine regimen Xing Qi Hua Ying Tang: a clinical study on 72 patients with multinodular and diffuse goiter.

J Altern Complement Med. Zhang A, Sun H, Wang P, Han Y, Wang X. Future perspectives of personalized medicine in traditional Chinese medicine: a systems biology approach. Complement Ther Med. Institute for Traditional Medicine.

Treatments for Thyroid Diseases with Chinese Herbal Medicine. Mayo Clinic. Yang H, Cong Y, Wu T, et al. Clinical Efficacy of Yingliu Mixture Combined with Methimazole for Treating Diffuse Goitre with Hyperthyroidism and Its Impact on Related Cytokines.

Pharmaceutical Biology, , doi: Treatment of Goiter with Traditional Chinese Medicine Regimen Xing Qi Hua Ying Tang: A Clinical Study on 72 Patients with Multinodular and Diffuse Goiter. HJ Altern Complement Med.

By Dr. Patrick Purdue Dr. Patrick Purdue, DOM has his Diplomate in Oriental Medicine and specializes in using acupuncture for internal medicine and pain management. Use limited data to select advertising. Create profiles for personalised advertising.

Use profiles to select personalised advertising. Create profiles to personalise content. Use profiles to select personalised content.

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Low T3 levels may indicate hypothyroidism, though again, T3 levels may be normal in subclinical hypothyroidism. Hypothyroidism is a lifelong condition. For many people, medication reduces or alleviates symptoms. Hypothyroidism is best treated by using levothyroxine Levoxyl, Synthroid.

This synthetic version of the T4 hormone copies the action of the thyroid hormone your body would normally produce.

The medication is designed to return adequate levels of thyroid hormone to your blood. Once hormone levels are restored, symptoms of the condition are likely to disappear or at least become much more manageable. You and your doctor will work together to find a dose and a treatment plan that best addresses your symptoms.

This can take some time. In most cases, people with hypothyroidism must remain on this medication their entire lives. To make sure your medication is still working properly, your doctor will likely test your TSH levels yearly.

Besides standard thyroid medications, animal extracts that contain thyroid hormone are also available. These extracts come from the thyroid glands of pigs.

They contain both T4 and triiodothyronine T3. Research has found medications with animal extracts to be similar to levothyroxine. Other studies have indicated that taking animal thyroid extract may reduce thyroid symptoms but cause more side effects.

You can also buy glandular extract supplements in some health food stores. Additionally, studies suggest that selenium supplements may help people with hypothyroidism caused by autoimmune disease, though research is mixed.

Use these products at your own risk. Complications of hypothyroidism include:. However, there are some recommendations to keep in mind. There are plenty of iodine-rich foods , including:. Soy may be linked to hypothyroidism. Drinking or eating too many soy products may lower thyroid function, especially in people with thyroid disorders.

However, more research in this area is needed. Fiber may interfere with thyroid hormone absorption. Too much dietary fiber may prevent your body from getting the hormones it needs from thyroid medications. Instead, avoid taking your medication within several hours of eating high fiber foods.

If you take supplements or medications in addition to thyroid medications, try to take them at different times. Hypothyroidism often goes along with conditions such as:. Despite taking medication, you may still experience fatigue from time to time.

A study found that yoga improved fatigue and other symptoms in a small group of people with hypothyroidism, though more research is needed. Since hypothyroidism can cause depression and fatigue, it may also make your relationships more challenging.

Some hospitals sponsor meetings for people with health conditions including hypothyroidism. Ask for a recommendation from your doctor and consider attending a meeting. Research indicates that online communities may also help strengthen social connections, provide a supportive space, and help people with chronic illnesses share advice.

This can cause a variety of symptoms, including fatigue, weight gain, and even depression. A small study found that 60 percent of participants with hypothyroidism exhibited some symptoms of depression. Hypothyroidism may cause a range of mental health difficulties.

This can make diagnosing hypothyroidism difficult. Before making a treatment plan for mental health issues, doctors may consider testing for an underactive thyroid. Depression and hypothyroidism can share several symptoms. These include:.

The two conditions also have symptoms that may distinguish them from one another. For hypothyroidism, problems such as dry skin, constipation, and hair loss are common. Depression is often a diagnosis made based on symptoms and medical history.

Low thyroid function is diagnosed with a physical exam and blood tests. If your depression is caused only by hypothyroidism, correcting the thyroid disorder should treat the depression. While hypothyroidism has long been associated with depression, a study suggested it may be associated with anxiety too.

Researchers evaluated people between the ages of 18 and 45 who had a known history of hypothyroidism. Using an anxiety questionnaire, they found that around 63 percent of them met the criteria for some form of anxiety. Larger and more focused studies on anxiety may help determine whether a true connection exists between hypothyroidism and anxiety.

People with thyroid problems can and very often do have healthy pregnancies. Still, hypothyroidism can pose a particular set of challenges for pregnancy.

Low thyroid function or unmanaged hypothyroidism during pregnancy can cause:. You can develop hypothyroidism while 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 people who never had thyroid problems before they were pregnant may develop them after having a baby.

This is called postpartum thyroiditis. In many cases, the condition resolves within 12 to 18 months , and medication is no longer required. However, around 20 percent of people with postpartum thyroiditis will need long-term therapy.

Continue to take your medication as prescribed. This ensures that the baby is getting enough thyroid hormone for their brain and nervous system to develop normally. Eating a balanced diet and taking multivitamins while pregnant can help you maintain a healthy pregnancy.

Aim to consume around micrograms of iodine each day through food or supplements. Remember to talk with your doctor before starting any new supplements. As a result, an underactive thyroid may lead to some weight gain. The more severe the condition is, the greater your weight gain is likely to be.

Most people will gain somewhere between 5 and 10 pounds. Properly treating the condition may lead you to lose any weight you gained while your thyroid levels were not treated. Symptoms of an underactive thyroid, including weight gain, often develop over a long period of time and may not be caused by a thyroid disorder alone.

Instead, it may indicate that your weight gain was the result of lifestyle or other conditions rather than low hormone levels. Work with a doctor, registered dietitian , or personal trainer to develop a healthy eating plan and exercise strategy to reach or maintain a moderate weight. Hypothyroidism and anemia may have similar symptoms , such as fatigue.

A doctor will run several tests to determine the underlying cause of your symptoms. This may include iron. Over time, this may lead to anemia. The authors of a review suggest that hypothyroidism may be linked with several types of anemia , such as normochromic normocytic, hypochromic microcytic, and megaloblastic types.

Your body naturally goes through changes as you get older. If you notice a significant difference in how you feel or how your body is responding, talk with your doctor to see whether a thyroid problem may be affecting you.

You may also benefit from joining a support group for people living with hypothyroidism. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. VIEW ALL HISTORY. Your thyroid gland is responsible for growth and metabolism in your body.

Here are 10 common signs and symptoms of hypothyroidism, or low thyroid…. While hypothyroidism is more common in adults, children can have it too. From slowed growth rate to poor muscle tone, here are symptoms all parents…. Common thyroid disorders include Hashimoto's disease, Graves' disease, and goiter.

Learn about their symptoms, diagnosis, and treatments. Here are some facts you should know about hypothyroidism and how it differs from hyperthyroidism. Standard treatment for hypothyroidism includes oral medication, but there are natural therapies too.

Read about the pros and cons of five natural…. While fertility may not be the first thing that comes to mind after your diagnosis, understanding the connection between hypothyroidism and fertility…. If left untreated, hypothyroidism can lead to a variety of issues, including heart problems, nerve damage, and infertility.

Changing your diet is a great way to help manage the symptoms of both PCOS and hypothyroidism. Let's look at some recipes and meal planning ideas. A Quiz for Teens Are You a Workaholic?

How Well Do You Sleep? Health Conditions Discover Plan Connect. Hypothyroidism Underactive Thyroid : Everything You Need to Know. Medically reviewed by Kelly Wood, MD — By Kimberly Holland — Updated on February 1, Share on Pinterest Illustration by Wenzdai Figueroa.

What is hypothyroidism? How common is hypothyroidism? What are the signs and symptoms of hypothyroidism? What causes hypothyroidism? What are the risk factors of hypothyroidism? How is hypothyroidism diagnosed?

Which medications are available to treat hypothyroidism? What alternative treatments may help hypothyroidism? FDA has approved the use of potassium iodide and cuprous iodide for salt iodization [ 19 ], whereas the WHO recommends the use of potassium iodate due to its greater stability, particularly in warm, damp, or tropical climates [ 3 ].

However, most salt intake in the United States comes from processed foods, and food manufacturers almost always use noniodized salt in these foods. If they do use iodized salt, they must list the salt as iodized in the ingredient list on the food label [ 9 ].

Specialty salts, such as sea salt, kosher salt, Himalayan salt, and fleur de sel, are not usually iodized.

Product labels will indicate if the salt is iodized or provides iodide. As shown in Table 2, noniodized sea salt provides virtually no iodine [ 8 ]. In dietary supplements, iodine is often present as potassium iodide or sodium iodide [ 20 ].

Supplements containing kelp, a seaweed that contains iodine, are also available. A small study found that people absorb potassium iodide almost completely Dietary supplements containing only iodine are also available, and many contain high doses, sometimes above the UL [ 20 ]. Many dietary supplements that contain iodine are listed in the Dietary Supplement Label Database from the NIH [ 20 ].

This database contains label information from tens of thousands of dietary supplement products on the U. The Total Diet Study TDS , an FDA monitoring program, provides estimated iodine intakes of the U.

population [ 23 ]. Through the TDS program, foods that represent the average U. diet are purchased and analyzed for several components, including iodine. These intakes meet or exceed the EAR for all groups.

TDS data do not include iodine that people obtain from the discretionary use of iodized salt [ 25 , 26 ]. Because many U. households use iodized salt, TDS data likely underestimate the true iodine intake of most U.

Iodine status is typically assessed using urinary iodine measurements. Spot urine iodine measurements are a useful indicator of iodine status within populations [ 28 , 29 ].

However, multiple hour urinary iodine or multiple spot urine measurements are more accurate for individuals [ 4 , 30 ]. Median urinary iodine concentrations, from spot samples collected as part of a large survey, can be used to characterize the iodine status of populations [ 31 ]. However, because spot samples are not a suitable indicator of individual iodine status [ 30 ], these measurements cannot be used to diagnose individual cases of iodine deficiency or to identify the proportion of a population with iodine deficiency or with excessive iodine intakes [ 31 ].

Urinary iodine measurements from NHANES have been used since to monitor the iodine status of the U. population [ 32 ]. Since the inception of the NHANES monitoring program, urinary iodine measurements have shown that the general U. population is iodine sufficient. Much of this decline was a result of decreased levels of iodine in milk due to the reduced use of iodine-containing feed supplements and iodophor sanitizing agents in the dairy industry [ 34 ] as well as the reduced use of iodate dough conditioners by commercial bakers.

The use of erythrosine, an iodine-containing food dye commonly used in fruit-flavored breakfast cereals, also decreased during this time [ 34 ] though it is unclear to what extent this change actually affected urinary iodine levels because the bioavailability of iodine from erythrosine has been found to be low [ 35 ].

This sharp decline in urinary iodine levels caused some concern during the late s that the iodine sufficiency of the U. population could be at risk if this trend continued [ 33 ]. More recent NHANES measurements indicate that urinary iodine levels have stabilized in the general U.

These values have essentially remained unchanged in the last three NHANES surveys, indicating that the dietary iodine intake of the general U. population has remained stable since [ 36 ].

Analyses of NHANES datasets from to indicate that a substantial portion of pregnant women in the United States are iodine insufficient.

Suboptimal iodine status during pregnancy has also been observed in Australia [ 39 ]. Pregnant women who do not consume dairy products may be particularly at risk of iodine insufficiency.

Overall, it appears that the general U. population has adequate iodine intake but that some pregnant women may be at risk for iodine deficiency. Continued national iodine monitoring is needed with more emphasis on population subgroups that are most susceptible to iodine deficiency disorders.

Iodine deficiency has multiple adverse effects on growth and development and is the most common cause of preventable intellectual disability in the world [ 41 ].

Iodine deficiency disorders result from inadequate thyroid hormone production secondary to insufficient iodine [ 5 ]. During pregnancy and early infancy, iodine deficiency can cause irreversible effects.

Under normal conditions, the body tightly controls thyroid hormone concentrations via TSH. TSH increases thyroidal iodine uptake from the blood and the production of thyroid hormone. However, very low iodine intakes can reduce thyroid hormone production even in the presence of elevated TSH levels.

Goiter is usually the earliest clinical sign of iodine deficiency [ 2 ]. In pregnant women, iodine deficiency of this magnitude can cause major neurodevelopmental deficits and growth retardation in the fetus as well as miscarriage and stillbirth [ 5 ].

Chronic, severe iodine deficiency in utero causes cretinism, a condition characterized by intellectual disability, deaf mutism, motor spasticity, stunted growth, delayed sexual maturation, and other physical and neurological abnormalities [ 5 ].

In infants and children, less severe iodine deficiency can also cause neurodevelopmental deficits such as somewhat lower than average intelligence as measured by IQ [ 1 , 42 , 43 ].

Mild to moderate maternal iodine deficiency has also been associated with an increased risk of attention deficit hyperactivity disorder in children [ 44 ]. In adults, mild to moderate iodine deficiency can cause goiter as well as impaired mental function and work productivity secondary to hypothyroidism.

Chronic iodine deficiency may be associated with an increased risk of the follicular form of thyroid cancer [ 45 ]. Historically, iodine deficiency was endemic in mountainous regions of the United States and Mexico, and in the so called goiter belt around the Great Lakes [ 46 ].

Thanks to a more national food supply, iodized salt, and other factors, overt iodine deficiency is now uncommon in North America. International efforts since the early s have dramatically reduced the incidence of iodine deficiency worldwide, but some groups of people are still at risk of inadequate iodine intake.

Iodine insufficiency remains a public health problem in 25 countries with a total population of about million people [ 47 ]. The following groups are among those most likely to have inadequate iodine status.

The use of iodized salt is the most widely used strategy to control iodine deficiency. Surveys indicate that many pregnant women in the United States might consume insufficient amounts of iodine even if they do not have signs or symptoms of overt iodine deficiency [ 36 ].

The impact, if any, of this insufficient intake on fetal development is not known. Seafood, eggs, milk, and milk products are among the best sources of iodine. Vegans, people with certain food allergies or lactose intolerance, and others who consume no or minimal amounts of these foods might not obtain sufficient amounts of iodine [ 49 , 50 ].

Iodine-deficient soils produce crops that have low iodine levels. Mountainous areas e. People living in these areas are at risk of iodine deficiency unless they consume iodized salt or foods produced outside the iodine-deficient area.

Consumption of foods that contain goitrogens, substances that interfere with the uptake of iodine in the thyroid, can exacerbate iodine deficiency [ 2 ]. Foods high in goitrogens include soy, cassava, and cruciferous vegetables e.

These issues are of concern primarily for people living in areas prone to iodine deficiency [ 6 ]. For most people, including most of the U. population, who have adequate iodine intakes and eat a variety of foods, the consumption of reasonable amounts of foods containing goitrogens is not a concern.

Due to its important role in fetal and infant development and thyroid hormone production, iodine is a critical nutrient for proper health at all life stages. Iodine sufficiency during pregnancy is extremely important for proper fetal development.

During early pregnancy, when fetal thyroid gland development is incomplete, the fetus depends entirely on maternal T4 and, therefore, on maternal iodine intake [ 52 ].

Sufficient iodine intake after birth is also important for proper physical and neurological growth and maturation. Research suggests that infants are more sensitive to the effects of iodine deficiency than other age groups, as indicated by changes in their TSH and T4 levels in response to even mild iodine deficiency [ 54 ].

Although severe iodine deficiency disorders are uncommon in the United States, mild to moderate iodine insufficiency during pregnancy may subtly affect fetal development [ 4 , ].

A meta-analysis of 6, mother-child pairs from three birth cohorts in the Netherlands, Spain, and the United Kingdom found that verbal IQ assessed in children at 1. Despite the importance of iodine for proper fetal development, the effects of iodine supplements during pregnancy on infant and child neurodevelopment in particular are inconclusive.

Iodine supplementation had no effect on child cognitive, language, or motor scores [ 62 ]. Breast milk contains iodine, although concentrations vary based on maternal iodine levels.

Infants who are exclusively breastfed depend on maternal iodine sufficiency for optimal development. During the weaning period, infants not receiving iodine-containing complementary foods may also be at risk of iodine deficiency, even in countries with iodized salt programs [ 64 , 65 ].

To ensure that adequate amounts of iodine are available for proper fetal and infant development, several national and international groups recommend iodine supplementation during pregnancy, lactation, and early childhood.

WHO recommendations for these countries also include breastfeeding through 24 months of age, combined with complementary foods fortified with iodine for children between the ages of 7—24 months [ 7 ]. Similarly, the American Academy of Pediatrics recommends that women who are pregnant, planning to become pregnant, or lactating take a daily supplement providing at least mcg iodine and use iodized salt [ 67 ].

The use of iodine-containing dietary supplements by pregnant and lactating women in the United States appears to be low compared to current recommendations. Of 59 best-selling prenatal multivitamin supplements on the market in —, only 34 contained iodine [ 22 ].

The median iodine content was mcg per daily serving, with a range of 25 to mcg; 25 of the 34 provided iodine as potassium iodide. According to — NHANES data, Results from a study, however, raise some questions as to the safety of widespread iodine supplementation in areas of relative iodine sufficiency.

These findings suggest that taking higher doses of supplemental iodine during pregnancy could induce thyroid dysfunction in some women and underscore the need for additional research into the effects on maternal thyroid function of iodine supplementation during pregnancy.

Many researchers, as well as the American Thyroid Association, stress the importance of continued iodine status monitoring among women of reproductive age [ 1 , 4 , 32 , 38 , 56 , 70 , 71 ]. The effects of severe iodine deficiency on neurological development are well documented.

Results from several studies suggest, for example, that chronic, moderate to severe iodine deficiency, particularly in children, reduces IQ by about 12—