Guidance

Iodine metabolism: migrant health guide

Advice and guidance on the health needs of migrant patients for healthcare practitioners.

Main messages

Iodine deficiency is very rare in the UK indigenous population, but it is the world’s most prevalent yet preventable, cause of growth and intellectual impairment, particularly during foetal, neonatal and infant development. It has a significant societal and soci-economic impact. Iodine deficiency also causes hypothyroidism and hyperthyroidism associated with goitre formation in both children and adults.

Iodine deficiency is on the verge of elimination globally, but large populations around the globe who live in regions where the soil is deprived of iodine may still be at risk.

Those migrants at greatest risk of iodine deficiency come from:

  • the northern Indian subcontinent
  • mountainous regions of Europe, China, and Africa
  • the Andean region in South America

Consider possible thyroid disorders in migrants from risk areas being the result of iodine deficiency, and seek expert endocrinological advice as necessary.

Background

Function

Iodine is essential for:

  • the production of thyroid hormones
  • normal neurological development

Sources

Dietary sources of iodine are all variable and include:

  • fish and shellfish
  • some fruit and vegetables (green and leafy)
  • cereals and grains
  • milk and dairy products

The concentration of iodine in plant foods, such as cereals and grains, is determined by iodine levels in the soil.

In the UK, milk and dairy products are now the main dietary sources of iodine (33% for adults in 2011) due to the widespread use of iodine in:

  • animal feed
  • and use of iodophors as a sterilant of cows teat and milking vessels

While salt is fortified with iodine in many countries, iodised salt is not widely available in the UK.

Iodine deficiency

Groups at risk of iodine deficiency

Populations who live in regions with iodine deficient soil are at risk of iodine deficiency. These areas include:

  • the northern Indian subcontinent
  • mountainous regions of Europe, China and Africa
  • the Andean region in South America

Effects of iodine deficiency

Iodine is an essential constituent of the hormones produced by the thyroid gland in the neck, and iodine deficiency can cause it to enlarge, a condition known as goitre.

During pregnancy, severe iodine deficiency can result in:

  • stillbirth
  • spontaneous abortion
  • congenital hypothyroidism

In children, iodine deficiency can impair neurological development.

In both children and adults, it can lead to:

  • hypothyroidism
  • hyperthyroidism

Excessive iodine intake

In some countries, excess iodine or iodide intake can disrupt thyroid function, resulting in the induction of:

  • hypothyroidism with or without goitre
  • hyperthyroidism (thyrotoxicosis)
  • changes in the incidence and types of thyroid malignancies

Responses of this type frequently occur where:

  • there is general high iodine intake
  • intervention has taken place to correct iodine deficiency

Testing and treatment

Consider the possibility that thyroid disorders in migrants from at risk regions may be due to iodine deficiency. This is the commonest cause of hypothyroidism worldwide and goitre is present:

If you suspect iodine deficiency, you can seek expert endocrinological advice on:

  • the interpretation of thyroid function tests
  • other considerations
  • management of the condition and treatment

Be advised that the dietary reference value for iodine is:

Adult RNI (Reference Nutrient Intake) = 0.14 mg/day.

Published 31 July 2014