A follow up study on iodine nutrition and goiter rate of residents in excessive iodine intaking areas after ceasing supplementation of iodized salt in Dezhou City Shandong Province in 2013 -2014

Abstract

Objective To investigate the status of iodine content and goiter rate of the residents in excessive iodine intaking areas in Dezhou of Shandong Province after ceasing supplementation of iodized salt. Methods In ten excessive iodine intaking counties (cities, districts) from 2013 to 2014, 300 residents were selected from each county (city, district) to examine their household salt iodine level. Five counties (cities, districts) were chosen as monitoring sites every year, which were divided in two groups according to water iodine levels (150 -300 and > 300 μg/L). One town that met the requirement in each group was chosen as a test site, one hundred children aged 8 -10 (50 male and 50 female) from each test site were selected to measure their household salt iodine level. If the household salt was confirmed a non-iodized salt, water samples and urine samples were collected. Water iodine and urinary iodine contents were measured by arsenic cerium catalytic spectrophotometry (WS/T 107-2006); thyroid volume was measured by B ultrasound. Results In 2013 and 2014, the rate of non-iodized salt was 96.1% (2 882/2 999) and 92.7% (2 781/3 000); goiter rate was 3.2% (16/506) and 24.7% (129/523) in Dezhou City. Totally 1 052 household drinking water samples were measured, the median of water iodine level was 221.8 μg/L (0.5 -1 073.6 μg/L). Totally 1 035 urine samples were measured, the median of urinary iodine level was 405.9 μg/L (19.3 -2 464.1 μg/L). In the two groups (water iodine was 150-300 and > 300 μg/L, respectively), the goiter rate was 11.6% (59/508) and 16.5% (86/521), the difference between them was statistically significant (χ2 = 4.86, P < 0.05). Urinary iodine level was proportional to household water iodine level (r = 0.475, P < 0.01). The median of children' s household water iodine level and median of children's urinary iodine level had a U curve relationship with goiter rate. Conclusions The measure of stopping to supply iodized salt in excessive iodine intaking areas in Dezhou is well implemented. Some monitoring sites have significant improvement. However, the harmful effects of excessive iodine intaking are still there in some areas. There is an U-curve relationship between water iodine level and goiter rate. At the same time, we should pay attention to iodine deficiency that might be caused by changing water iodine content. Key words: Iodine; Water; Urine; Thyroid