Serum iodine levels and influencing factors of adults with different thyroid health conditions / 中华地方病学杂志

ABSTRACT

Objective:To explore the medical reference values, distribution characteristics and influencing factors of serum iodine in adults with different thyroid health conditions, and to evaluate the importance of serum iodine in evaluating individual iodine nutrition.Methods:From February 2017 to November 2018, multi-stage stratified cluster sampling was used to select one community and one agricultural (fishing) village in the coastal Yingkou City and the inland areas of Shenyang City of Liaoning Province as survey sites. Cluster sampling of adults over 18 years old who had lived for five years were conducted with questionnaire survey, clinical physical examination and thyroid ultrasound examination. Fasting venous blood samples and one random urine sample were collected from all subjects for serum iodine, thyroid hormone, antibody and urine iodine detection. The 95% medical reference value of serum iodine was established by using the percentage quantile method, and the reference value, distribution characteristics and influencing factors of serum iodine in adults with different thyroid health status were analyzed. The diagnostic value of iodine nutritional indicators in thyroid diseases was evaluated by the receiver operating characteristic (ROC) curve.Results:A total of 2 931 adults were surveyed, with serum iodine levels of 62.1 (53.6, 72.2) μg/L, ranging from 5.6 to 642.3 μg/L; urine iodine was 167.6 (111.2, 244.2) μg/L, and the overall iodine level was at an appropriate level. A total of 1 089 patients with thyroid diseases were examined, with a detection rate of 37.2% (1 089/2 931); among them, there were 597 cases of thyroid nodules, 56 cases of endemic goiter, 42 cases of hypothyroidism, 161 cases of subclinical hypothyroidism, 27 cases of hyperthyroidism, 18 cases of subclinical hyperthyroidism, and 474 cases of autoimmune thyroid disease (AITD). There was a statistically significant difference in the detection of thyroid diseases among adults with different levels of serum iodine (χ 2 = 13.80, P < 0.05). The reference values of serum iodine in normal adults, hypothyroidism (without thyroid hormone intervention), hyperthyroidism (without anti thyroid hormone drug treatment), AITD, endemic goiter, and thyroid nodules were 37.2 - 103.0, 12.5 - 52.8, 49.9 - 163.1, 34.3 - 129.3, 27.3 - 92.8, and 37.9 - 119.5 μg/L, respectively. The ROC curve analysis results showed that the serum iodine area under curve(AUC) of patients with hyperthyroidism, subclinical hyperthyroidism, endemic goiter, thyroid nodules, and AITD were 0.94, 0.61, 0.55, 0.53, and 0.52, respectively. The results of univariate analysis showed that there were statistically significant differences in adult serum iodine levels among different positions, regions, age, education level, occupation, iodine intake, blood pressure, and body mass index ( P < 0.05). Conclusions:There are significant differences in serum iodine levels among adults with different thyroid health conditions, and evaluation standards and systems should be developed separately. Serum iodine is an important indicator for evaluating individual iodine nutrition.