Evaluation of nitrate influence on thyroid volume of adults in a previously iodine-deficient area

Abstract

Objective: The aim of the present study was to analyze the influence of nitrate as a possible alimentary goitrogen on thyroid volume in a previously iodine-deficient area. Design: Population based cross-sectional epidemiologic survey. Participants: Data of 3772 participants (20–79 years) of the Study of Health in Pomerania without diagnosed thyroid disorders were analyzed. Evaluation and measurements: The nitrate concentration in spot urine was determined by ion chromatography. High nitrate levels were defined as urine nitrate concentrations exceeding the 75th percentile for the investigated population. Thyroid structure and size were measured by ultrasound. Subjects were divided into two groups with absence or presence of high urine nitrate concentrations. Comparisons between groups were made using the χ 2-test or the Student's t-test. Multivariable analyses were done by logistic regression and ANOVA (analysis of variance). Odds ratios and their 95% confidence intervals as well as adjusted means (standard error) were calculated. Results: In the whole population, the mean urine nitrate level was 53.1±0.8 mg/l. The 75th percentile of urine nitrate concentrations was 69.0 mg/l, indicating that the renal excretion of nitrate is at a low level. The proportion of goiter in subjects with and without high urine nitrate concentrations was 35.5% and 34.7%, respectively ( p=0.69). Analyses considering age, sex and further potential confounders could not identify an association between the exposure variable and the risk of goiter. Conclusion: The low level of the alimentary nitrate intake does not influence the thyroid volume in a population with currently sufficient alimentary intake of iodine.