UK survey finds that 69% of a sample of teenage schoolgirls have some degree of iodine deficiency
- Correspondence to Steven Boyages
Department of NSW, Clinical Education and Training Institute, Sydney, NSW 2124, Australia;
Implications for nursing practice and research
■ Nurses need to understand the importance of iodine for normal thyroid physiology.
■ Nurses need to be aware that teenage schoolgirls may have some degree of iodine deficiency and, if this is the case, provide appropriate dietary advice.
■ Further research is needed to test the relationship of urine iodine levels to clinical outcome measures such as thyroid size measured as total goiter prevalence.
■ Future studies should examine at population outcome measures of thyroid function and size.
Iodine is an essential micronutrient for the production of thyroid hormones. In states of low-iodine intake, the thyroid gland undergoes adaptive changes to conserve and increase uptake of iodine to maintain thyroid hormone production. This is clinically evident in mild states of iodine deficiency such as thyroid enlargement or goiter.1 In severe states of iodine deficiency, thyroid hormone levels are compromised and during pregnancy these perturbations of maternal and fetal thyroid hormone levels lead to irreversible damage of fetal neurodevelopment. This may manifest as neuropsychological deficits (such as IQ potential) in its mildest forms to major deficits, termed endemic cretinism, in its extreme forms.2
Iodine deficiency disorders (IDDs) still remain a major public health problem in 54 countries.3 A total of 285 million school-age children and nearly two billion individuals worldwide have been estimated to have an insufficient iodine intake. It is estimated that the total goiter prevalence in the general population globally is 15.8%.
Vanderpump et al conducted a cross-sectional survey that assessed iodine status in schoolgirls aged 14–15 years attending secondary school in nine UK centres. A total of 810 girls were assessed. Urinary iodine concentrations and tap water iodine concentrations were measured in June to July 2009 and November to December 2009. Ethnic origin, postcode and a validated diet questionnaire assessing sources of iodine were recorded.
The study showed that schoolgirls in the UK may be classified as living in mild iodine deficiency with a median level of urinary iodine (UI) of 80.1 mcg/l. Sufficient iodine intake is defined as a median UI level of 100 mcg/l or above. This study indicates that IDDs may pose a public health risk in the UK.
The present study strongly reaffirms the findings from Australia and the USA that iodine deficiency may re-emerge in developed nations, if population sources of iodine are not maintained and or if the status of a population is not regularly monitored.4 IDDs were highly prevalent in many nations at the turn of the 20th century but were largely controlled through systematic prophylaxis programmes. In other nations such as the UK and Australia, improvement in iodine status was largely accidental.
Mild iodine deficiency usually manifests as an increased rate of goiter prevalence only and is not thought to have consequences on neurological development. Our previous studies that demonstrated an impact of iodine deficiency on IQ were undertaken in populations groups that lived in states of severe iodine deficiency (UI levels<20 mcg/l).
However, undertaking surveys of iodine status using single spot urine iodine levels is only useful at the population level and cannot be used to assess individual iodine status. Previous studies have well-documented evidence related to the pitfalls and controversies of measurement of urine iodine status.5 Therefore, comments about individual iodine status in the present study need to be interpreted with extreme caution.
What should happen next in the UK with these findings? This study should be followed up by future studies that look at population outcome measures of thyroid function and size (measured by thyroid ultrasound).6 If iodine deficiency is confirmed then the solution of food fortification is relatively simple.