Iodine status in European women in New Zealand with moderate selenium deficiency

Abstract

For the optimal function of thyroid gland, adequate intakes of iodine and selenium are required. Since iodine is essential component of the thyroid hormones, its insufficiency leads to inadequate hormone production and further to inadequate tissue response (hypothyroidism), goitre, stillbirth and miscarriages, and growth retardation. According to the World Health Organisation the recommended median urinary iodine concentrations (UIC) are the best indicators of iodine nutrition. The WHO defines iodine sufficiency in an adult population as a median UIC of > 100 µg/L in spot urine samples. Iodine deficiency was and still is a problem in New Zealand. In September 2009 the mandatory fortification of all bread with iodized salt was introduced. Therefore, the primary aim of the study was to determine the levels of iodine in both groups, and the secondary aim of the study was to determine whether there is a relationship between selenium and iodine, and iodine and thyroid hormones in two groups of European women. Urinary iodine concentration was determined in spot samples by the new method called "Fast B", which is improved Sandell-Kolthoff reaction. The results of the study showed the mean urinary iodine level in the control group and the group of women with the Hashimoto's thyroiditis was 120.77± 59.35 (median UIC was128.00 µg/L), and 98.64 ± 62.83 (median UIC was 95.00 µg/L), respectively. Estimated daily iodine intake of 150µg/ day was achieved in five participants in the control group, and four participants in the group of women with Hashimoto's thyroiditis. Estimated median iodine intake in the control group and Hashimoto's group was 142.22 and 105.55, respectively, indicating mild iodine deficiency. There was no significant relationships found between iodine and selenium, and iodine and thyroid hormones in both groups. The results of the current study are in line with the results from larger studies carried out in New Zealand. Iodine intakes appear to have improved after the mandatory fortification of bread with iodised salt in 2009, although iodine deficiency is still a problem in New Zealand. Using an iodine fortified bread clearly made an impact on the overall iodine intake but not to the expected level. There was no association found between iodine and selenium, and iodine and thyroid hormones. Any possible interaction between selenium and iodine is still unclear.