What diseases can you get from iodine?

November 24, 2025 •

4 min read

According to the World Health Organization, iodine deficiency is the single most common cause of preventable mental impairment globally. However, an excess of this essential mineral can also trigger severe health problems, predominantly affecting the thyroid gland. Understanding this delicate balance is critical for preventing a wide range of conditions linked to both too little and too much iodine.

Quick Summary

This guide details the wide spectrum of diseases caused by both insufficient and excessive iodine intake. The article explains how iodine levels impact thyroid function and lead to conditions such as goiter, hypothyroidism, hyperthyroidism, and autoimmune disorders like Hashimoto's disease and Graves' disease. Additionally, it covers the severe developmental consequences of deficiency and the acute risks of iodine toxicity.

Key Points

Iodine Deficiency Leads to Hypothyroidism: Without sufficient iodine, the thyroid cannot produce enough hormones, causing symptoms like fatigue, weight gain, and an enlarged gland known as goiter.
Iodine Excess Can Also Cause Thyroid Dysfunction: High iodine intake can trigger both hypothyroidism (via the Wolff-Chaikoff effect) and hyperthyroidism (via the Jod-Basedow effect), especially in susceptible individuals.
Both Deficiency and Excess May Induce Autoimmunity: Autoimmune thyroid conditions, such as Graves' and Hashimoto's disease, can be exacerbated or triggered by iodine imbalance.
Deficiency Causes Severe Developmental Problems: Severe iodine deficiency during pregnancy can cause cretinism, resulting in permanent intellectual disability and stunted growth in children.
Sources of Excess Include Supplements and Medications: While food-based excess is less common, high doses from dietary supplements, certain medications (like amiodarone), and contrast media can cause toxicity.
Balanced Intake is Critical: The relationship between iodine intake and thyroid health follows a 'U-shaped curve,' meaning both too little and too much can be harmful.
Vulnerable Populations Need Careful Monitoring: Pregnant women, infants, and individuals with existing thyroid disease require special attention to ensure their iodine intake is within a safe range.

The Dual Nature of Iodine: Deficiency and Excess

Iodine is a trace mineral vital for synthesizing thyroid hormones, which regulate metabolism, growth, and development. The human body cannot produce its own iodine, making dietary intake essential. However, the health risks associated with iodine form a 'U-shaped curve,' where problems arise from both insufficient intake (deficiency) and excessive consumption (excess). The thyroid gland's adaptive mechanisms can be overwhelmed by chronic imbalance, leading to various disorders. While global salt iodization efforts have significantly reduced deficiency disorders, poor monitoring and environmental factors can still lead to localized issues of both deficiency and excess.

Diseases Caused by Iodine Deficiency

Iodine deficiency remains a major global public health concern, particularly in landlocked and mountainous regions where soil is naturally low in iodine. A persistent lack of iodine triggers a cascade of issues as the body attempts to compensate.

Goiter: This is often the first visible sign of iodine deficiency, characterized by an enlarged thyroid gland in the neck. The gland swells as it attempts to trap more iodine from the bloodstream to produce thyroid hormones.
Hypothyroidism: An underactive thyroid results from severe, prolonged deficiency, as it can no longer produce enough thyroid hormone. Symptoms include weight gain, fatigue, dry skin, constipation, and increased sensitivity to cold.
Cretinism: Severe maternal iodine deficiency during pregnancy can cause congenital hypothyroidism, leading to cretinism in the infant. This condition is marked by permanent intellectual disability, growth retardation, deaf-mutism, and other severe neurological abnormalities.
Developmental Delays: Even mild to moderate iodine deficiency during pregnancy and early childhood is linked to subtle cognitive impairments, including lower IQ and impaired neurodevelopment.
Pregnancy Complications: Deficiency increases the risk of serious complications like miscarriage, stillbirth, and infertility.

Diseases Caused by Iodine Excess

While less publicized than deficiency, excessive iodine intake can also lead to thyroid disorders and other health problems, particularly for susceptible individuals with pre-existing thyroid conditions or past deficiencies.

Iodine-Induced Hypothyroidism: In certain sensitive individuals, including those with autoimmune thyroiditis, excess iodine can inhibit thyroid hormone synthesis via the "Wolff-Chaikoff effect" and lead to an underactive thyroid.
Iodine-Induced Hyperthyroidism: A sudden increase in iodine, often from supplements or certain medications, can cause an overactive thyroid, a phenomenon known as the "Jod-Basedow effect". Symptoms include a rapid heart rate, anxiety, and weight loss.
Autoimmune Thyroiditis: Both Hashimoto's thyroiditis (leading to hypothyroidism) and Graves' disease (leading to hyperthyroidism) have been linked to an increased iodine intake, particularly in iodine-sufficient populations. Excess iodine may trigger or worsen these conditions by altering the immune response.
Thyroid Cancer: Studies have shown that both iodine deficiency and chronic excess can increase the risk of certain types of thyroid cancer, such as papillary thyroid cancer.
Acute Iodine Poisoning: While rare, ingesting extremely high doses of iodine can be toxic. Symptoms include burning in the mouth and stomach, fever, abdominal pain, nausea, and vomiting.

Comparison Table: Iodine Deficiency vs. Iodine Excess Disorders


Feature	Iodine Deficiency Disorders	Iodine Excess Disorders
Primary Cause	Insufficient dietary iodine intake.	Overconsumption from supplements, diet (e.g., seaweed), or medication.
Mechanism	Thyroid enlarges to capture more iodine, or hormone production falls.	Disrupts the thyroid's regulatory systems, sometimes causing autoimmune responses.
Associated Thyroid Conditions	Goiter, Hypothyroidism, Cretinism.	Goiter, Hyperthyroidism, Autoimmune Thyroiditis.
Neurological Effects	Cognitive impairment, lower IQ, permanent intellectual disability.	Potential neurotoxic effects; impaired learning and memory.
Maternal & Fetal Risks	Increased miscarriage, stillbirth, cretinism.	Risk of thyroid problems in the baby.
Populations at Risk	Those in endemic iodine-deficient areas; pregnant and breastfeeding women.	Susceptible individuals with pre-existing thyroid issues; individuals with high seafood consumption.

Achieving Optimal Iodine Balance

Managing iodine intake is a public health priority that involves balancing the risks of both deficiency and excess. In many developed nations, mandatory or voluntary salt iodization programs ensure that the majority of the population receives adequate iodine. However, shifting dietary habits, such as reduced salt consumption or the increased use of non-iodized salt in processed foods, can complicate this balance.

For individuals, the source and quantity of iodine can vary widely. Seafood, dairy products, and eggs are natural sources. Seaweed and kelp supplements contain extremely high and variable concentrations of iodine, which can be a significant source of excess. Additionally, medications like amiodarone and iodinated contrast media used in medical procedures can lead to iodine overload. Special attention is needed for vulnerable groups, including pregnant women, infants, and individuals with existing thyroid conditions, who are more sensitive to fluctuations in iodine levels. Medical guidance is always recommended before starting supplementation.

Conclusion

Iodine is a double-edged sword: essential for life but dangerous in imbalanced amounts. The spectrum of diseases, from cretinism caused by severe deficiency to autoimmune thyroiditis exacerbated by excess, highlights the importance of maintaining an appropriate intake. While universal salt iodization has been a highly effective strategy for preventing widespread deficiency, continuous monitoring of both iodine intake and thyroid health is necessary. For anyone concerned about their iodine status, including pregnant women and those with pre-existing thyroid conditions, consulting a healthcare provider is the safest approach. Ensuring a balanced intake is a crucial step toward safeguarding long-term thyroid and overall health.

Frequently Asked Questions

The most common disease from too little iodine is goiter, an enlargement of the thyroid gland, which is the body's attempt to capture more iodine to produce thyroid hormones.

Yes, high iodine intake can cause the thyroid to become underactive (hypothyroidism) in some individuals. This occurs due to the Wolff-Chaikoff effect, a temporary inhibition of thyroid hormone synthesis.

Yes, excessive iodine intake has been linked to the development or worsening of autoimmune thyroid diseases like Hashimoto's and Graves' disease, particularly in populations with a history of iodine deficiency or existing thyroid issues.

Iodine deficiency during pregnancy can lead to serious conditions like miscarriage, stillbirth, and cretinism in the baby, which causes permanent intellectual and developmental disabilities.

Iodine poisoning from food alone is very rare. It typically results from consuming very high doses from dietary supplements or certain medications. However, excessive consumption of very iodine-rich foods like seaweed can lead to thyroid problems over time.

Severe iodine deficiency during fetal development can cause cretinism, resulting in permanent intellectual disability. Even mild to moderate deficiency can be linked to lower IQ and subtle neurodevelopmental delays in children.

Vulnerable populations include pregnant and breastfeeding women, infants, the elderly, and individuals with pre-existing thyroid conditions, as they are more sensitive to fluctuations in iodine levels.