Status of iodine nutrition and thyroid function of healthy adults in urban and rural areas of Xi'an City / 中华地方病学杂志

ABSTRACT

Objective To find out the iodine nutrition and thyroid function of adults in rural and urban areas of Xi'an City, and to analyze the relationship between iodine intake and thyroid function. Methods Two streets ( townships ) were selected in urban and rural areas of Xi'an City according to multi-stage stratified cluster sampling, one community (administrative village) was selected in each street (township), and 100 residents were selected from each community (administrative village). Drinking water, household salt, urine and blood samples of people over the age of 16 were collected to test water iodine, salt iodine, urinary iodine and thyroid function. Results A total of 354 drinking water samples were examined, and the median of water iodine was 4.50 μg/L in Xi'an, and iodine concentrations of ≥10 μg/L in urban group was higher than that of rural group [ 48 . 21％ ( 94/195 ) vs 20.13％ (32/159), χ2= 30.123, P < 0.05]. The highest value of urban water iodine was 244.10 μg/L. A total of 354 edible salt samples were examined, and the median of salt iodine was 19.62 mg/kg in urban and rural areas of Xi'an. The edible rate of qualified iodized salt in urban group was higher than rural group [78.97％(154/195) vs 69.18％(110/159),χ2=12.523,P<0.05]. The median of urinary iodine of urban and rural groups were 236.00 and 196.00μg/L, respectively, and urban group was higher than rural group (Z = - 3.121, P < 0.05). The frequency distribution of urinary iodine in urban group was different from rural group (χ2=24.440,P<0.05). The mean value of thyroxine (T4) in urban group was lower than that of rural group,and there was statistical difference [nmol/L:(89.43 ± 19.70) vs (93.57 ± 16.89), t = - 2.098,P < 0.05]. The positive rates of anti-thyroglobulin antibody (TgAb) of urban and rural groups were 21.54％(42/195) and 13.21％(21/159), the positive rate of TgAb was higher in urban than in rural (χ2=4.155, P < 0.05). The positive rates of thyroid peroxidases antibody (TPOAb) were 13.33％ (26/195) and 6.92％(11/159), respectively. There were no statistically significant differences of thyroid dysfunction in urban and rural groups [14.87％(29/195) vs 12.58％(20/159), P > 0.05]. Subclinical hypothyroidism in all thyroid dysfunction was the main thyroid disorder, which was 7.18％(14/195) and 6.92％ (11/159) in urban and rural groups. Conclusions Xi'an urban healthy adult iodine intake is at an ultra-appropriate level. In rural areas, the intake of iodine in healthy adults is at an appropriate level. The areas of high water iodine are found in Xi'an for the first time. Increased iodine intake may promote the occurrence of subclinical hypothyroidism.