Effects of different concentrations of iodized salt on iodine nutrition and thyroid function of children and pregnant women / 中华地方病学杂志

ABSTRACT

Objective To assess iodine nutrition and thyroid function in children and pregnant women before and after iodized salt concentration decline,and investigate the appropriate concentration of iodized salt.Methods Cluster sampling was carried out,study areas in Shandong and Gansu provinces were selected according to the coverage rate of iodized salt which was more than 95％ and the levels of iodine and fluoride in drinking water which were less than or equal to 10 μg/L and 1 mg/L,respectively in 2012 and 2014.Before (2012) and after (2014) iodized salt concentration declinechildren and pregnant women were selected;salt,drinking water and urinary samples were collected;the iodine content of salt,the iodine and fluoride content of drinking water,and urinary iodine were tested.B ultrasound was used to examine the thyroid volume and the total goiter rate (TGR) was calculated in children.The blood sample was collected to test thyrotropin (TSH) and thyroglobulin (Tg) in the 2 groups of subjects.Results Before iodized salt concentration decline,the children median urinary iodine (MUI) concentrations of Shandong and Gansu provinces were 291.4 and 321.9 μg/L,which at the over appropriate and overdose levels,respectively.MUI of Shandong and Gansu provinces were 220.5 and 274.7 μg/L in pregnant women,which were at adequate and over appropriate levels.After iodized salt concentration decline,MUI of Shandong and Gansu provinces were 199.8 and 178.2 μg/L in children,and were 178.6 and 159.2 μg/L in pregnant women,which were all at adequate levels.Children's TGR declined from 7.95％ (7/88) to 5.88％ (7/119) in Shandong Province,children's TGR rose to 5.77％ (6/104) from 2.06％ (2/97) in Gansu Province,there was no statistical differences (x2 =0.34,1.81,P ＞ 0.05).Before and after iodized salt concentration decline,there were no differences statistically in TSH levels of children and pregnant women in Shandong and Gansu provinces (Z =-1.08,-0.83,-1.30,-0.80,P ＞ 0.05).Mter iodized salt concentration decline,the Tg levels were significantly lower than that before intervention in children and pregnant women in Shandong Province (Z =-10.78,-7.04,P ＜0.01);the Tg level was increased than that before intervention in pregnant women group in Gansu Province (Z =-2.78,P ＜ 0.01).Conclusion After iodized salt concentration declined,iodine nutrition and thyroid function status of Shandong Province are reasonable,but the indicators of Gansu Province have a trend of iodine deficiency,monitoring needs to be strengthened,and iodized salt content needs to be adjusted in time.