New research suggests the UK population is now iodine-deficient and a full review and evidence-based recommendations are needed to safeguard public health. The findings, presented today at the Society for Endocrinology annual conference, provide the only current data on the UK's iodine status and demonstrate iodine-deficiency in a large sample population. Iodine-deficiency is the most common cause of preventable mental impairment worldwide.

In the study, which was funded by the Clinical Endocrinology Trust and is the first of its kind in the UK, Dr Mark Vanderpump (Royal Free Hampstead NHS Trust) and colleagues on behalf of the British Thyroid Association measured urinary iodine levels in samples from 737 14-15 year old girls from nine UK centres. Factors that might skew the results (e.g. diet, ethnicity) were assessed using a questionnaire. Variations due to season and location were corrected for via measurements taken in Summer 2009 and Winter 2009/2010 and water samples from each area were measured for iodine content.

The median urinary iodine level in participants was 80μg/L, making the group 'deficient' by World Health Organisation standards (defined as below 100μg/L). 69% of the samples were in this deficient category (below 100ug/L) and 18% of samples showed very low iodine levels below 50μg/L.

As this was a relatively small audit study that was confined to a single age group and sex, a full-scale investigation into the iodine status of the entire UK population is now warranted to see whether public health bodies need to implement any health measures.

Iodine is an essential trace element which helps the thyroid gland function properly. Most people get their iodine from their diet. Iodine-deficiency is the most common cause of preventable mental impairment worldwide and accordingly, the World Health Organisation has conducted a global programme of salt iodisation since 1993. The UK is yet to join this programme and does not require salt producers to iodise their salt.

Young women of childbearing age are the most susceptible to the adverse effects of iodine-deficiency and even mild deficiency may have an impact on the developing brain of foetuses and young children. It can also cause goitre. According to the World Health Organisation, iodine-deficient communities have IQs up to 13.5 points lower than similar but iodine-sufficient communities1.

Researcher Dr Mark Vanderpump, Consultant Physician and Honorary Senior Lecturer in Diabetes and Endocrinology at the Royal Free Hampstead NHS Trust said:

"Our data suggest the UK is now iodine deficient, warranting a full investigation of the UK iodine status. We need to look into this now to decide whether public health bodies need to step in.

"The World Health Organisation has made iodine-deficiency a global priority and has been campaigning for at-risk countries to add iodine to their salt, a campaign which has been very successful. If it turns out that we do have a problem, this could be the most viable solution.

"We are very concerned about these findings as the consequences of iodine-deficiency are grave: iodine-deficient communities score lower in IQ tests, and even mild iodine-deficiency during pregnancy can cause serious mental impairments in children."

Notes

This research will be presented as a lecture by Dr Mark Vanderpump at the Society for Endocrinology BES meeting on Tuesday 12 April 2011 at 10:00am. The abstract for this talk is reproduced here.

1 World Health Organisation. 2007. Assessment of iodine deficiency disorders and monitoring their elimination.

The Society for Endocrinology BES 2011 conference is Britain's biggest scientific meeting on hormones, and is taking place at the Birmingham ICC from 11-14 April 2011. For the full programme, please click here.

The British Thyroid Association is a non-profit learned society of accredited doctors and scientists with an interest in the thyroid gland and thyroid disease.

Abstract

Assessment of the UK Iodine Status: A National Survey

Mark Vanderpump1, John Lazarus2, Peter Smyth3, Robert Burns3, Margaret Eggo4, Thang Han1, Graham Williams5, Barbara Torlinska4, Karen Mullan6, Simon Pearce7, Salman Razvi8, Mike Lean9, Emile C Aspray9, Denise Bannon10, Prakash Abraham11, Bijay Vadia12, Graham Leese13, Peter Laurberg14, Kristien Boelaert4, Jayne Franklyn4,

1Royal Free Hampstead NHS Trust, London, United Kingdom; 2University Hospital Wales, Cardiff, United Kingdom; 3University College, Dublin, Ireland; 4University of Birmingham, Birmingham, United Kingdom; 5Imperial College, London, United Kingdom; 6Royal Infirmary, Belfast, United Kingdom; 7University of Newcastle, Newcastle-upon-Tyne, United Kingdom; 8Gateshead Health NHS Foundation Trust, Gateshead, United Kingdom; 9University of Glasgow, Glasgow, United Kingdom; 10Institute of Medical Genetics, Glasgow, United Kingdom; 11Aberdeen Royal infirmary, Aberdeen, United Kingdom; 12Royal Devon and Exeter Hospital, Exeter, United Kingdom; 13University of Dundee, Dundee, United Kingdom; 14Aalborg Hospital, Aalborg, Denmark

Inadequate dietary iodine intake is the most common cause of preventable mental impairment worldwide and is defined by the WHO as a population median urinary iodine (UI) excretion <100 μg/L. No contemporary data are available for the UK according to the ICCIDD. The UK has no programme of food/salt iodination.

We have performed a systematic assessment of the current UK iodine status in 14-15 year old schoolgirls. 810 participants from nine UK centres provided 737 urine samples. UI concentrations were measured as µg iodine/L by a multiplate persulphate digestion method followed by Sandel-Kolthoff colorimetry in specimens collected in Summer 2009 and Winter 2009/2010. Ethnicity, postcode and a diet questionnaire assessing sources of iodine were recorded. Iodine concentrations were also measured in water samples from each area.

The median UI value for this sample was 80 µg/L with 69% of samples <100 µg/L and 18% <50 µg/L. A multivariate regression analysis confirmed as independent factors a difference in summer versus winter iodine status (R-squared value 0.2, p<0.001) with the median nadir of 76µg/L in summer and a positive association with milk intake (R-squared value 0.2, p<0.001). There was no correlation with other foods, ethnicity or city of origin.

These findings suggest that the UK is now iodine-deficient, consistent with a fall in iodine status recently reported in Australia and USA. Young women of child-bearing age are the most susceptible to the adverse effects of iodine deficiency. Even mild perturbations of fetal and maternal thyroid function have an impact upon neurodevelopment so these findings are consequently of huge public health importance. These findings indicate an urgent need for a comprehensive investigation of UK iodine status and evidence based recommendations on the need to implement a policy of iodine prophylaxis.

Source:
Society for Endocrinology