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. 2021 Feb;60(1):493-502.
doi: 10.1007/s00394-020-02268-3. Epub 2020 May 11.

Spot urine iodine levels below the WHO recommendation are not related to impaired thyroid function in healthy children and adolescents

Tillmann Wallborn  1   2 , Mandy Vogel  3 , Antje Kneuer  4 , Michael Thamm  4 , Katalin Dittrich  5 , Wieland Kiess  5   3 , Jürgen Kratzsch  6
Affiliations

Spot urine iodine levels below the WHO recommendation are not related to impaired thyroid function in healthy children and adolescents

Tillmann Wallborn et al. Eur J Nutr. 2021 Feb.

Abstract

Purpose: Iodine deficiency in childhood and adolescence may lead to later thyroid dysfunction, stunted growth and cognitive impairment. The World Health Organization (WHO) has issued recommended age-dependent urine iodine concentration targets, but a critical threshold beyond which clinical sequelae are to be expected remains undefined. Our study aimed to investigate spot urine iodine concentration in a typical Central European cohort of children and adolescents, and consider the implications of these values in regard to laboratory parameters for evaluating thyroid function.

Methods: Using the Sandell-Kolthoff method, spot urine iodine concentration was measured cross-sectionally from 1802 healthy children and adolescent in the age range of 0.25-18 years within the LIFE-Child epidemiological study based in and around the city of Leipzig (Germany). Additionally, serum thyroid biomarkers of these subjects were measured and correlated to urine iodine levels.

Results: In our cohort, 61.39% of boys and 65.91% of girls had an iodine level of < 100 µg/L (57%, 67%, 65% of the age groups 0-5, 6-12 and 13-18 years), the median iodine excretion was 86 µg/L in boys and 80 µg/L in girls. The iodine levels revealed no significant correlation with the thyroid biomarkers TSH, FT4 and FT3. Moreover, iodine values revealed no correlation with levels of antibodies against thyroid peroxidase or thyroglobulin.

Conclusion: In our cohort of children and adolescents, the relatively high number of iodine levels below the WHO recommendation appears not to be related to clinical or subclinical thyroid diseases in the respective participants.

Keywords: Children; FT3; FT4; Iodine; TSH; Thyroid; Urine.

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Conflict of interest statement

All authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Figures

Fig. 1
Fig. 1
Spot urine iodine concentration of all participants by age and gender with percentiles
Fig. 2
Fig. 2
Creatinine SDS and spot urine iodine levels of all participants according to the WHO classification. Creatinine-SDS were calculated for each age group and compared to WHO iodine categories. Participants with higher urine creatinine levels also presented higher iodine levels
Fig. 3
Fig. 3
TSH distribution in high-, medium- and low- spot urine iodine groups. TSH (thyrotropin) distribution in three different groups [small dots: individuals with low spot urine iodine (< − 1.28 SDS), continuous line: individuals with medium spot urine iodine (− 1.28 to + 1.28 SDS), broad dots: individuals with high spot urine iodine (> + 1.28 SDS)]. TSH is slightly shifted towards right side in individuals with lower iodine excretion
Fig. 4
Fig. 4
Spot urine iodine in high-, middle- and low-FT4 groups. Participants were separated into three groups based on FT4 (free thyroxine) level (< − 1.28 SDS, − 1.28 to + 1.28 SDS, >  + 1.28 SDS) and their spot urine levels compared. The numbers on the bars indicate the significance level. Individuals with different FT4 levels presented no significant difference in iodine excretion
See this image and copyright information in PMC

References

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