OVERVIEW

What is iodine deficiency disorder?

A group of diseases caused by iodine deficiency is called iodine deficiency disorder.

Depending on the severity of iodine deficiency, the age at which it occurs, and individual responses to iodine deficiency, iodine deficiency disorder can manifest in various ways, such as endemic goiter (enlarged thyroid) and endemic cretinism, both of which fall under the category of iodine deficiency disorder.

The key treatment is iodine supplementation, along with addressing other consequences caused by iodine deficiency.

Iodine deficiency disorder poses a significant threat to a nation's population quality, making prevention crucial. Iodized salt is a convenient and effective preventive measure.

Is iodine deficiency disorder common?

In the past, iodine deficiency disorder was common both in China and abroad. After China implemented a nationwide policy of salt iodization, cases of newborns affected by iodine deficiency disorder have become rare.

SYMPTOMS

What are the typical manifestations of iodine deficiency disorders?

• Endemic goiter
  Iodine deficiency in adulthood can lead to goiter, an enlargement of the thyroid gland that helps it synthesize sufficient thyroid hormones to meet the body's needs.
  In high-altitude mountainous areas and inland regions far from the sea, soil and water sources are often iodine-deficient. Many people living in these areas develop goiter, hence the term "endemic goiter," also known as "big neck disease."
  In the early stages of iodine deficiency, the thyroid usually enlarges uniformly, referred to as "diffuse goiter." Prolonged iodine deficiency can lead to the formation of nodules on the thyroid, known as "nodular goiter."
• Endemic cretinism
  In iodine-deficient regions, if women do not consume enough iodine during pregnancy and/or after the birth of the fetus, it can not only cause neonatal goiter but also impair the growth and development of the newborn, leading to intellectual disabilities, stunted growth, deafness, strabismus, paralysis, abnormal gait, and other symptoms, collectively termed "endemic cretinism."
• Miscarriage, premature birth, stillbirth, and congenital malformations
  Maternal iodine deficiency can result in miscarriage, premature birth, stillbirth, congenital malformations, and fetal hypothyroidism.
  Severe iodine deficiency during infancy can lead to early death.

Besides the symptoms mentioned above, what other problems can iodine deficiency cause?

• Hypothyroidism
  If the enlarged thyroid can produce enough thyroid hormones, thyroid function may remain normal. However, if the enlarged thyroid still cannot meet the body's demand for thyroid hormones, hypothyroidism (commonly referred to as "underactive thyroid") may occur.
  Hypothyroidism can cause fatigue, lethargy, cold intolerance, swelling, poor appetite, weight gain, constipation, drowsiness, and menstrual irregularities.
• Hyperthyroidism
  In patients with nodular goiter, the thyroid may develop autonomous function. When these patients receive iodine supplementation, their thyroid may produce and secrete excessive thyroid hormones uncontrollably, leading to hyperthyroidism (overactive thyroid).
  Hyperthyroidism can cause heat intolerance, excessive sweating, palpitations, hand tremors, increased appetite, weight loss, frequent bowel movements, insomnia, irritability, and menstrual irregularities.
• Thyroid follicular carcinoma
  In regions with endemic goiter, the risk of thyroid follicular carcinoma is also increased, which research suggests is linked to iodine deficiency.

CAUSES

What is the daily recommended intake of iodine?

The World Health Organization (WHO) recommends:

• Infants and children ≤ 5 years old: 90 micrograms of iodine per day.
• Children aged 6–12: 120 micrograms of iodine per day.
• Children ≥ 12 years old and adults: 150 micrograms of iodine per day.
• Pregnant and breastfeeding women: 250 micrograms of iodine per day.

The human body can obtain iodine through diet, drinking water, and respiration.

What are the functions of iodine?

Iodine is a crucial raw material for synthesizing thyroid hormones. Thyroid hormones promote growth and development in children, maintain normal body temperature, aid in nutrient metabolism, and regulate heart function.

How does iodine deficiency disorder occur?

The root cause of iodine deficiency disorder is insufficient iodine, leading to inadequate thyroid hormone production, which results in a series of symptoms and manifestations.
Additionally, other factors can trigger or worsen iodine deficiency disorder, including:

• Goitrogenic substances: Common examples include cruciferous vegetables, cassava, millet, sorghum, high-fluoride drinking water, and high-calcium drinking water.
• Nutritional deficiencies: Such as lack of animal protein (meat, eggs, dairy), zinc deficiency, selenium deficiency, or vitamin A deficiency.

Who is more susceptible to iodine deficiency disorder?

• Infants and children: Their growth and development require large amounts of thyroid hormones. Iodine deficiency during this period can lead to severe consequences like intellectual disabilities, stunted growth, deafness, and paralysis.
• Pregnant and breastfeeding women: Pregnant women lose more iodine through urine, and they need to supply iodine to the fetus or infant, making them prone to deficiency. Iodine deficiency during this time can cause maternal goiter, as well as adverse pregnancy outcomes like miscarriage, premature birth, and stillbirth.

Why do people with iodine deficiency disorder in the same iodine-deficient region exhibit different symptoms?

• The age at which iodine deficiency occurs determines the manifestations.

For example, iodine deficiency during fetal development may lead to miscarriage, premature birth, stillbirth, or congenital deformities; in infancy, it may cause intellectual impairment, stunted growth, deafness, or muteness; in adults, it mainly manifests as goiter.

• Individual sensitivity to iodine deficiency varies, leading to different manifestations.

For instance, among iodine-deficient adults, some may develop goiter, while others show no abnormalities.

DIAGNOSIS

How to determine iodine deficiency disorders? How to diagnose iodine deficiency?

For individual patients, doctors primarily assess iodine deficiency by evaluating dietary habits and considering local iodine distribution (i.e., whether local water and soil are iodine-deficient or iodine-rich).
For populations, iodine deficiency can be diagnosed by measuring urinary iodine concentration. If the average daily iodine intake is 150 micrograms, the urinary iodine concentration is approximately 100 micrograms per liter.

How to assess population iodine deficiency using urinary iodine levels?

Select a population group and randomly sample a number of individuals to measure their urinary iodine concentrations, then calculate the median.
A median urinary iodine concentration meeting the following standards indicates sufficient iodine intake:

• Children and non-pregnant adults: 100–299 micrograms per liter;
• Pregnant women: 150–249 micrograms per liter.

A median urinary iodine concentration in the following ranges indicates iodine deficiency:

• 50–99 micrograms per liter: mild iodine deficiency;
• 20–49 micrograms per liter: moderate iodine deficiency;
• < 20 micrograms per liter: severe iodine deficiency.

TREATMENT

How to treat iodine deficiency disorders?

The root cause of iodine deficiency disorders is lack of iodine, so the key to treatment lies in iodine supplementation. However, for patients with endemic cretinism, brain damage such as intellectual disability, deaf-mutism, and abnormal posture can no longer be reversed, whether through iodine supplementation or direct thyroid hormone replacement. Therefore, prevention is more important than treatment for iodine deficiency disorders.

What are the forms of iodine supplementation in the treatment and prevention of iodine deficiency disorders?

Iodine supplementation can take many forms, including iodized salt, iodized water, iodine-containing medications, dietary iodine intake, and iodine-fortified foods.

• Iodized salt: The preferred method of iodine supplementation, where potassium iodide or potassium iodate is added to salt. The latter is more stable and easier to store.
• Iodized water: Can serve as a temporary iodine supplementation method. It is simple to implement—just a few drops of iodine added to drinking water over the long term.
• Iodine-containing medications: Such as iodized oil, potassium iodide solution, or potassium iodide tablets. Suitable for people in areas without iodized salt programs or for additional iodine supplementation in pregnant or breastfeeding women.
• Dietary iodine intake: Consuming iodine-rich seafood like kelp, seaweed, shellfish, etc., can also supplement iodine. However, this method makes it difficult to control dosage and is less stable.
• Iodine-fortified foods: For example, enhancing the iodine uptake rate in spinach or other vegetables (such as tomatoes and potatoes). This is still in the research stage.

Can iodine supplementation cause adverse reactions in patients with iodine deficiency disorders?

In most cases, as long as iodine supplementation is not excessive, it will not cause adverse reactions.

However, for patients with endemic goiter (especially nodular goiter), iodine supplementation may lead to hyperthyroidism, which poses certain risks for older individuals or those with cardiovascular diseases.

Additionally, for patients with autoimmune thyroiditis, iodine supplementation may trigger hypothyroidism. Overall, the benefits of iodine supplementation outweigh the risks.

DIET & LIFESTYLE

How to Properly Store and Use Iodized Salt?

Iodized salt should be stored in a cool, dry place, away from direct sunlight and high temperatures near stoves. It is not advisable to store it for too long. It is recommended to purchase small packets of salt and buy as needed.

During cooking, salt should be added when the food is almost done. Avoid using salt for high-heat stir-frying or prolonged stewing to minimize iodine loss.

PREVENTION

How to Prevent Iodine Deficiency Disorders?

The cause of iodine deficiency disorders is clear—lack of iodine.

Therefore, iodine supplementation can prevent this condition.

• In most regions of China, soil and drinking water are generally iodine-deficient. At this stage, maintaining iodized salt consumption (except in a few areas with high water iodine levels) remains the most effective measure to prevent iodine deficiency disorders.
• Additionally, for high-risk groups with greater iodine needs, such as pregnant women and developing infants, increasing the proportion of iodine-rich foods—such as consuming more seaweed, kelp, and other seafood—can also play a significant role.