Iodine Deficiency
Key points
- Iodine deficiency can lead to growth and developmental abnormalities, hypothyroidism, goiter and thyroid disease.
- Global prevalence of iodine deficiency is high.
- Iodine deficiency is caused by dietary insufficiency and is more common in regions that lack iodine fortification programs or are far from the sea.
Prevalence
The global prevalence of iodine deficiency is high: about 2 billion people worldwide, including one-third of school-aged children.1 The prevalence is greater in regions where there is a lack of iodine fortification in foods such as salt. This is especially significant in regions that are far away from a sea or ocean.
Definition
Iodine deficiency is caused by dietary insufficiency. Because ingested iodine is primarily excreted in urine, urinary iodine concentration is a good indicator of iodine intake.2 Epidemiological criteria for iodine deficiency used by the World Health Organization in school-aged children are summarized in Table 1.
| Median urinary iodine, mg/L | Iodine intake | Iodine nutrition |
|---|---|---|
| < 20 | Insufficient | Severe iodine deficiency |
| 20–49 | Insufficient | Moderate iodine deficiency |
| 50–99 | Insufficient | Mild iodine deficiency |
| 100–199 | Adequate | Optimal |
| 200–299 | More than adequate | Risk of iodine-induced hyperthyroidism within 5–10 years following introduction of iodized salt in susceptible groups |
| > 300 | Excessive | Risk of adverse health consequences (iodine-induced hyperthyroidism, autoimmune thyroid diseases) |
| Source: World Health Organization. Assessment of iodine deficiency disorders and monitoring their elimination: A guide for programme managers, 2/e. ©WHO, 2001. All rights reserved. | ||
Consequences
Iodine deficiency in pregnancy can lead to physical and mental retardation of the infant (cretinism). In infants and children it can lead to growth and developmental abnormalities, hypothyroidism, and goiter, often the result of long-term iodine deficiency (months to years). Iodine deficiency is the most prevalent cause of thyroid disease globally.1
Diagnosis
Iodine deficiency can be assessed in a number of ways, such as:3
- Serum thyroid stimulating hormone (TSH), free T3 and T4: Sensitive indicators of iodine status.
- Serum thyroglobulin: Reflects iodine intake over a longer term (weeks to months).
- Urinary iodine concentration: A sensitive indicator of recent iodine intake (days).
- Ultrasound of the thyroid to detect goiter.
Treatment
Information on recommended daily intakes of iodine for all age groups, including infants, children and adolescents, are available from Health Canada.
Selected resources
- Centers for Disease Control and Prevention. Immigrant and refugee health.
- Health Canada, 2007. Eating well with Canada’s food guide is available in multiple languages.
- U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases. Guidelines for evaluation of the nutritional status and growth in refugee children during the domestic medical screening process. Bethesda, MD: CDC, April 2012.
References
- Centers for Disease Control and Prevention. Guidelines for evaluation of the nutritional status and growth in refugee children during the domestic medical screening examination. Bethesda, MD: CDC, 2012.
- Centers for Disease Control and Prevention, World Food Programme. A Manual: Measuring and interpreting malnutrition and mortality. Rome: WFP, 2005.
- Zimmerman MB. Iodine deficiency. Endocrine Rev 2009;30(4):376-408.
Editor(s)
- Anna Banerji, MD
- Andrea Hunter, MD
Last updated: May, 2013