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Caring for kids new to Canada

A guide for health professionals working with immigrant and refugee children and youth

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.


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.


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.

Table 1: Epidemiological criteria for assessing iodine nutrition based on median urinary iodine concentrations in school-aged children
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.


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


Iodine deficiency can be assessed in a number of ways, such as:3

  1. Serum thyroid stimulating hormone (TSH), free T3 and T4: Sensitive indicators of iodine status.
  2. Serum thyroglobulin: Reflects iodine intake over a longer term (weeks to months).
  3. Urinary iodine concentration: A sensitive indicator of recent iodine intake (days).
  4. Ultrasound of the thyroid to detect goiter.


Information on recommended daily intakes of iodine for all age groups, including infants, children and adolescents, are available from Health Canada. 

Selected resources


  1. 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.
  2. Centers for Disease Control and Prevention, World Food Programme. A Manual: Measuring and interpreting malnutrition and mortality. Rome: WFP, 2005.
  3. Zimmerman MB. Iodine deficiency. Endocrine Rev 2009;30(4):376-408.


  • Anna Banerji, MD
  • Andrea Hunter, MD

Last updated: May, 2013