Letter: Iodine Status in Filipino Women of Childbearing Age (Endocrinol Metab 2018;33:372-9, Michael E. Serafico et al.)

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Endocrinol Metab. 2018;33(4):493-494
Publication date (electronic) : 2018 November 30
doi : https://doi.org/10.3803/EnM.2018.33.4.493
1Department of Health and Environmental Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, China.
2School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Malaysia.
3Health and Sustainability Innovation (HSI) Lab, Health Technologies University Research Centre (HT-URC), Xi'an Jiaotong-Liverpool University, Suzhou, China.
Corresponding author: Zheng Feei Ma. Department of Health and Environmental Sciences, Xi'an Jiaotong-Liverpool University, Suzhou 215123, China. Tel: +86-512-8188-4938, Fax: +86-512-8188-4938, Zhengfeei.Ma@xjtlu.edu.cn
Received 2018 October 11; Accepted 2018 October 13.

This letter is regarding the recent article “Iodine status in Filipino women of childbearing age” by Serafico et al. [1]. The findings presented by the authors are both interesting and relevant to iodine assessments conducted in Asia, particularly in the Philippines. Since 1995, the implementation of the Act for Salt Iodization Nationwide (ASIN Law) has improved the iodine status of Filipinos. The authors' cross-sectional study covered 17 regions, involving 80 provinces in the Philippines. A total of 6,194 women were asked to provide a casual urine sample for the determination of urinary iodine concentration (UIC). Overall, the authors reported that the median UIC of Filipino women was 123 µg/L, which indicated sufficient iodine intake (median UIC, 100 to 199 µg/L) [2].

Although the study had a relatively large sample size, it had some limitations that were not addressed by the authors. For example, although the collection of spot urine samples for the determination of UIC is relatively easy to perform, UIC has high intra- and inter-individual variation [3]. In addition, UIC also depends on hydration status, and urinary creatinine measurements should be included to correct for this [3]. Therefore, future studies should consider including the measurement of other biomarkers of iodine status, such as thyroid-stimulating hormone, thyroglobulin, and thyroid hormone levels, in order to enable a more comprehensive assessment of population iodine status [234], particularly in Asian populations. Furthermore, the use of iodized salt in populations should be reported [5]. Studies have shown that populations living along the coast may be at risk of consuming excess iodine in their diet [5]. Therefore, low coverage of iodized salt is usually reported in these coastal areas [5], which explains why some population groups remain iodine-deficient despite the implementation of a universal salt iodization program.


CONFLICTS OF INTEREST: No potential conflict of interest relevant to this article was reported.


1. Serafico ME, Ulanday JRC, Alibayan MV, Gironella GMP, Perlas LA. Iodine status in Filipino women of childbearing age. Endocrinol Metab (Seoul) 2018;33:372–379. 30229576.
2. Pearce EN. Chapter 2, Assessment of population iodine status. Iodine deficiency disorders and their elimination Cham: Springer; 2017. p. 15–28.
3. Ma ZF, Venn BJ, Manning PJ, Cameron CM, Skeaff SA. The sensitivity and specificity of thyroglobulin concentration using repeated measures of urinary iodine excretion. Eur J Nutr 2018;57:1313–1320. 28285430.
4. Ma ZF, Venn BJ, Manning PJ, Cameron CM, Skeaff SA. Iodine supplementation of mildly iodine-deficient adults lowers thyroglobulin: a randomized controlled trial. J Clin Endocrinol Metab 2016;101:1737–1744. 26891118.
5. Ma ZF. A comparative study of iodized salt programs: Shanghai and Switzerland. Biol Trace Elem Res 2018;8. 14. [Epub]. 10.1007/s12011-018-1478-8.

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