Thyroid status in pregnant women and association with nitrates as an environmental factor stimulating the manifestation of iodine deficiency

Objective: The purpose of this study was to assess the thyroid status of pregnant women on the basis of biochemical indicators and to look for association between nitrates as an environmental factor and the manifestation of iodine deficiency. Materials and methods: Subjects of the research were 116 pregnant women from the town and district of Plovdiv in Southern Bulgaria. Urinary iodine, thyroid-stimulating hormone (TSH), free thyroxin (FT4), and serum nitrate levels were measured. Results: More than half of the pregnant women (59.3%) had iodine deficiency, 5.8% and 19.0% had deviations in the values of TSH and FT4, respectively. The median serum nitrate level in pregnant women was 20.79 (95% CI 20.49 - 24.9) mu mol/L. The evaluation of the relationship between frequency of iodine deficiency and the values of serum nitrate in inspected pregnant women revealed that the association was statistically significant: OR = 4.266 (95%CI 1.589 - 11.452); chi(2) = 9.08, p = 0.0029. Conclusion: This study found a significant correlation between urinary iodine, TSH and FT4 in the pregnant women. It confirmed the possible role of a high nitrate level in food and drinking water as a risk factor for thyroid dysfunction in this vulnerable population group.