High Iodine Urinary Concentration Is Associated with High TSH Levels but Not with Nutrition Status in Schoolchildren of Northeastern Mexico

Aidy Gonzalez-Nunez,Marcela Vela-Amieva,Augusto Rojas-Martínez,Pablo García-Solís,Silvia G Ramirez-Garcia,Victor J Lara-Díaz,German Flores-Ramirez

doi:10.3390/nu13113975

Abstract

According to the Iodine Global Network, Mexico is considered a country with adequate national iodine intake (297 mg/L), but some regions have not been studied. We aimed to evaluate urinary iodine concentration (UIC) and its association with thyroid stimulating hormone (TSH) levels and the nutritional status in 307 children (aged 5 to 11 years) from three elementary schools of Monterrey, northern Mexico. UIC in spot urine samples and capillary TSH levels were measured to assess thyroid function, in addition to weight, height, body mass index (BMI), and waist circumference (WC). We found a median UIC of 442 mg/L and a significant association between UIC and TSH levels by logistic regression when data were adjusted for (1) age and sex; (2) age, sex, and WC; and (3) age, sex, and weight status. UIC values were higher in 7-year-old children compared to 11-year-old children. High prevalences of overweight/obesity (41%) and WC >90 pctl (22%) were observed. This study identified higher UIC levels in children than those previously reported in the country. The UIC showed a positive and significant correlation between TSH levels in the three models evaluated. More studies are needed to assess the causes and possible outcomes of high UIC levels.

Highlights

According to the Iodine Global Network, Mexico is considered a country with adequate national iodine intake (297 mg/L), but some regions have not been studied
Iodine deficiency is considered to have been eradicated in the Americas and this region reports the highest proportion of households consuming iodized salt during the past two decades, 12 out of 24 countries in this area report iodine intake above the requirements [3,4]
Schoolchildren are prevalence of goiter, median of urinary iodine concentration (UIC), and thyroglobulin (Tg), a thyroid protein, a precursor in the synthesis of thyroid hormones, that is increased in thyroid hyperplasia and goiter; thyroid stimulating hormone (TSH) levels in dry blood samples, is the preferred indicator in neonates [6]

Summary

Introduction

According to the Iodine Global Network, Mexico is considered a country with adequate national iodine intake (297 mg/L), but some regions have not been studied. We aimed to evaluate urinary iodine concentration (UIC) and its association with thyroid stimulating hormone (TSH) levels and the nutritional status in 307 children (aged 5 to 11 years) from three elementary schools of Monterrey, northern Mexico. Schoolchildren are prevalence of goiter (palpation/ultrasound), median of urinary iodine concentration (UIC), and thyroglobulin (Tg), a thyroid protein, a precursor in the synthesis of thyroid hormones, that is increased in thyroid hyperplasia and goiter (characteristic of iodine deficiency); thyroid stimulating hormone (TSH) levels in dry blood samples, is the preferred indicator in neonates [6]. The UIC median is a useful indicator to assesses recent iodine intake at population level [6]

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Discussion

Conclusion