Population Status of Iodine and Its Potential Effects on Thyroid Function and Autoimmunity in Southwestern Colombia

Background: This study aimed to investigate the iodine status and its potential effects on thyroid function and autoimmunity in Colombia.

Methods: This was a cross-sectional study, in population of urban and rural areas, from four geographic regions in the Department of Cauca, Colombia; the participants were 412 healthy adults, a third from rural areas. The following variables were evaluated: median urinary iodine concentration (mUIC), serum thyrotropin (TSH), clinical and ultrasonographic (US) goiter assessment, and anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-Tg) and anti-TSH receptor (TRAb) concentrations.

Results: The mUIC levels were 153.9 µg/L (interquartile range (IQR): 220.06); 30% had "excessive" mUIC and a quarter had "low" mUIC. The positivity of anti-Tg and anti-TPO was higher in subjects > 60 years (P = 0.017 and P ≤ 0.001, respectively). A high prevalence of "low" mUIC was found in the "low" socioeconomic status (SES) and of "more than adequate or excessive" in the "high" SES when compared with the "medium" SES (P ≤ 0.001). The prevalence of goiter by physical examination was 41.7% and 34% by US. The highest mUIC levels were significantly more prevalent in women, in subjects with elevated TSH and in those from rural areas.

Conclusions: The population status of iodine in Colombia is U-shaped; the high prevalence of goiter, hypothyroidism, and thyroid autoimmunity can be explained by excess or deficit of iodine and by probable environmental goitrogens.