Study on the relationship between serum iodine and dysfunctions: a cross-sectional study

The relationship between serum iodine and thyroid dysfunctions in male and female adults is poorly understood. This study aimed to explore the relationship between serum and urine iodine and thyroid dysfunction in male and female adults. A total of 1320 participants were included in the final analysis. We collected basic demographic information, as well as blood and spot urine samples, to determine serological indices and iodine nutritional status of subjects. The median (IQR) of UIC, UIC/UCr, SIC were 155.8 (94.5, 211.1) µg/L, 138.1 (91.1, 207.6) µg/g and 70.6 (59.8, 83.9) µg/L, respectively. SIC was positively correlated with UIC and UIC/UCr ( P  < 0.001, P  < 0.001). The prevalence of hypothyroidism and subclinical hypothyroidism in female was significantly higher than that in male ( P  = 0.02, P  = 0.002). In male subjects, subjects with SIC༞97.1 µg/L had a higher risk of hyperthyroidism (OR = 2.91, 95% CI: 1.38, 6.19) and overt hypothyroidism (OR = 5.59, 95% CI: 1.88, 6.42). In female subjects, subjects with SIC < 49.3 µg/L had a higher risk of overt hypothyroidism (OR = 2.18, 95% CI: 1.10, 4.06), TgAb positive (OR = 1.97, 95% CI: 1.15, 3.32) and TPOAb positive(OR = 2.48, 95% CI: 1.41, 4.26). In conclusion, serum iodine can be used as an indicator to evaluate iodine nutritional status and thyroid dysfunctions. Higher serum iodine concentration was associated with an increased risk of hyperthyroidism and overt hypothyroidism in men, lower serum iodine concentration was associated with an increased risk of overt hypothyroidism and positive TgAb and TPOAb in women.