Objective To understand the prevalence of thyropathy among the residents of Jiaojiang District and related iodine nutrition condition.
Methods A cross-sectional design survey was conducted among residents of 311 households in 3 villages by stratified cluster sampling from April through June. A total of 944 subjects were registered to urinary iodine test (arsenic-cerium catalyzed spectrophotometry) and 793 to type-B ultrasound thyroid examination. Other tests included chemiluminesent immunoassay for thyroid hormone and direct titration for iodine in table salt.
Results The thyroid nodule rate was 22.95% (182/793) and increased with age (χ2=72.12, P=0.001). The difference of thyroid nodule rate between the 6-14 years group (0.00%) and the ≥15 years group (25.60%) was statistically significant (χ2=27.24, P=0.001), and that between female (26.79%) and male (17.82%) was also found statistically significant (χ2=9.25, P=0.002). No enlarged thyroid was found in the 31 children (8-10-year-old). The prevalence rate of thyroid nodule in the group of urinary iodine <100 μg/L was higher than that in the group of urinary iodine ≥100 μg/L (χ2=12.50, P=0.007). The standardized prevalence rates in Baiguo Village, Gaozhang Village and Huajing Village were 19.44%, 26.43% and 19.42% respectively. The median urinary iodine (MUI) of all 944 residents was 178.25 μg/L, with 185.85 μg/L for the children investigated, 138.50 μg/L for the pregnant females, 181.40 μg/L for the lactating females, 176.00 μg/L for the general population, 184.40 μg/L for Baiguo Village, 152.00 μg/L for Gaozhang Village and 192.00μg/L for Huajing Village. Among the pregnant females examined, 6.06% (2/33) were found positive in both thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb). Among the 178 participants with B-type ultrasonic abnormalities, an elevated free triiodothyronine (FT3) was found in 171 cases (96.07%); elevated free thyroxine (FT4) and total thyroxine (TT4) were found in 178 cases (100.00%); an elevated total triiodothyronine (TT3) in 159 case (89.33%); thyrotropin (TSH) abnormality showed in 11 cases (3 reduced, 8 increased) (6.18%); TgAb-positive and TPOAb-positive were found in 27 cases (15.17%). The iodized salt coverage rate of the 311 households surveyed was 77.50%, of which 90.30% were qualified iodized salt, the consumption rate of qualified iodized salt was 74.34%, and the mean of iodine content in salt was 28.74 mg/kg. Of the 9 tap water samples, the median of iodine content was 2.2 μg/L.
Conclusion The iodine condition is generally acceptable in Jiaojiang District, but not sufficient among pregnant women. The hypothesis regarding iodized salt as the cause of thyroid nodules is not supported by available evidences.
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