A study on the medical reference value of serum iodine and its correlation with thyroid function indicators in adults with normal thyroid function in Liaoning Province / 中华地方病学杂志

ABSTRACT

Objective:To learn about the levels of serum iodine and thyroid function indicators in adults with normal thyroid function in Liaoning Province, to establish the medical reference value range of serum iodine, and to explore the relationship between serum iodine and thyroid function indicators.Methods:From February 2017 to December 2018, one subdistrict and one rural township were selected as the survey sites in the coastal area (Gaizhou City of Yingkou) and inland area (Kangping County of Shenyang) of Liaoning Province, respectively. Permanent residents aged 18 and older who have lived there for 5 years or more were selected as the survey subjects. Blood samples were collected to test the levels of serum iodine and thyroid function indicators [thyroid stimulating hormone (TSH), free triiodothyronine (FT 3), free thyroxine (FT 4), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb)]. The percentile method was used to establish the 95% medical reference value range of serum iodine in adults with normal thyroid function, and Pearson correlation analysis was used to analyze the correlation between serum iodine and thyroid function indicators. Results:A total of 1 621 adults with normal thyroid function were examined, the median serum iodine was 62.0 μg/L, and the 95% medical reference value range was preliminarily determined as 37.0-103.0 μg/L. Among them, the medians serum iodine of males and females (826 and 795 cases) were 62.3 and 61.0 μg/L, respectively, and there was no significant difference between genders ( Z=- 1.26, P = 0.210). The medians serum iodine of adults in coastal and inland areas (827 and 794 cases) were 61.7 and 61.9 μg/L, respectively, and there was no significant difference between areas ( Z = - 0.16, P = 0.870). The medians serum iodine of adults aged 18 - 29, 30 - 39, 40 - 49, 50 - 59 and 60 - 80 (385, 392, 378, 253 and 213 cases) were 61.0, 61.0, 63.0, 65.0 and 62.0 μg/L, respectively, and the difference between ages was statistically significant ( H = 14.52, P = 0.006). Pearson correlation analysis showed that serum iodine was weakly correlated with the level of FT 4 ( r = 0.17, P < 0.001), but not with the levels of TSH, TPOAb and TgAb ( P > 0.05). Conclusions:This study has established the medical reference value range of serum iodine in adults with normal thyroid function in Liaoning Province. Serum iodine is not correlated with the levels of TSH, TPOAb and TgAb.