A preliminary study on medical reference range of serum iodine in adults of normal thyroid function

Objective To explore the iodine nutrition and medical reference range of serum iodine in adults of normal thyroid function, and to provide scientific evidence for individual iodine nutritional assessment. Methods Totally 244 postgraduate freshmen were selected in one university, which is located in Harbin, Heilongjiang Province. Adults of normal thyroid function were recruited, excluding the adults of abnormal thyroid function and other diseases. The following indicators were adopted to assess iodine status: arsenic cerium catalytic spectrophotometry (WS/T 107.1-2016) was used to detect urinary iodine, perchloric acid and sodium cholrate resolution method was used to detect serum iodine, chemiluminescence immune assay was used to detect free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), thyroglobulin antibody (TGAb), thyroid peroxidase antibody (TPOAb). To assess these indicators and conduct correlation analysis. Results A total of 185 adults with normal thyroid function were chosen, the level of urinary iodine [M (P25, P75)] was 140.40 (90.30, 198.95) μg/L. The average level of serum iodine was (66.32 ± 15.46) μg/L for the adults of normal thyroid function, the 95% medical reference range of serum iodine in normal adults was initially formulated as 36.02-96.62 μg/L. The average level of FT3 in adults of normal thyroid function was (5.18 ± 0.51) pmol/L, the average level of FT4 was (18.04 ± 2.06) pmol/L, and the level of TSH was 1.57 (1.14, 2.04) mU/L. The area under the receiver operating characteristic (ROC) curve for serum iodine was 0.781, it was higher than the area under ROC curve for urinary iodine (0.524), the difference was statistically significant (t =-12.22, P 0.05). Conclusions Serum iodine, which can accurately reflect recent iodine nutritional status, is relatively stable than urinary iodine. The medical reference range of serum iodine in normal adults is formulated in this study and it may provide scientific evidence for individual iodine nutritional assessment. Key words: Adults; Serum; Iodine; Reference values