The Philippines is one of the countries where adequate iodine status has been achieved. However, iodine deficiency still remains an important public health problem in this country. In this study, we evaluated iodine nutrition status and investigated an awareness status of iodine deficiency targeting high school students of Tuguegarao, Philippines. A total of 260 students provided samples for urinary iodine analysis, among which 146 students completed thyroid volume measurement by ultrasonography and answering the questionnaires. The median urinary iodine level was 355.3
Over the past two decades, global iodine nutrition status has markedly been improved. According to the International Council for Control of Iodine Deficiency Disorders (ICCIDD), the number of iodine deficient countries was decreased from 54 countries in 2003 to only 32 countries in 2011 [
The Philippines has been overcoming iodine deficiency through government policies such as ASIN law which mandated the addition of iodine to all salt for animal and human consumption since 1995 [
In this study, we examined urinary iodine concentrations and thyroid volumes to evaluate iodine nutrition status among high school students in Tuguegarao, Philippines. We also investigated an awareness status of iodine deficiency using questionnaires to identify the areas we need to further focus on, in order to eliminate iodine deficiency in the country.
This study was conducted on high school students in Tuguegarao, Cagayan Valley, Philippines, in July 2013. A total of 260 high school students provided samples for urinary iodine analysis, among which 146 students (median age = 15, range 12–25) completed measuring thyroid volume by ultrasonography and answering questionnaires for awareness of iodine deficiency. Among them, 79 (54.1%) were girls and 67 (38.4%) were boys.
This study was approved by the Institutional Review Board (IRB) of Kosin University College of Medicine. The study was also approved by the mayor of Tuguegarao and Cagayan State University, Cagayan, Philippines. Informed consent was obtained from the subjects. Height (cm) and weight (kg) were measured for all the participants, and body surface area (BSA) was calculated by the following formula [
The spot urine samples (4.0 to 11.5 mL) were collected from 260 students in wide-mouthed screw capped plastic bottles. The samples were immediately filtered and refrigerated until analysis. Urinary iodine (UI) concentrations were determined by modified microplate method employing ammonium persulfate digestion followed by Sandell-Kolthoff reaction [
Thyroid volumes were measured using a portable ultrasound instrument equipped with a 10 MHz linear transducer (LOGIQ BOOK XP, GE healthcare, Seoul, Republic of Korea). The examination was performed by a single experienced endocrinologist with two additional persons assisting and record-keeping. The subjects were in the supine position with the hyperextension of neck for examination. The volume of each lobe was calculated using the following formula [
The questionnaires consisted of five main questions and two subquestions: (1) have you heard about the problems associated with iodine deficiency in the environment and insufficient intake of iodine in the human body?; (2) can you list some problems (disorders) resulting from iodine deficiency?; (2-1) which problems (disorders)? (please select all you can list); (3) where do you receive information about iodine deficiency disorders and preventing them?; (4) what do you need to do about iodine deficiency?; (5) do you buy iodized salt?; (5-1) (if you answered “no” to question (5) what is (are) the reason(s) you do not buy iodized salt?
For each subject, the observed measurements were carried out by an experienced endocrinologist. The thyroid volume was represented by the value of minimum, maximum, median, and mean ± standard deviation according to age. We compared urine iodine levels with the previous National Nutritional Survey (NNS) data of 1998 and 2003 by descriptive statistics. Between the two groups who use iodized salt and do not use iodized salt, urinary iodine, thyroid volume, height, and weight were compared by dependent
A median urinary iodine level was 355.3
Urinary iodine concentration from a total of 260 high school students in Tuguegarao.
Median | Mean | 95% confidence interval of mean | Maximum | Minimum | Number of iodine deficiency (%) <100 |
|
---|---|---|---|---|---|---|
Urinary iodine ( |
355.3 | 378.5 | 352.5–407.9 | 1402.69 | 29.27 | 10 (3.8%) |
Cr adjusted iodine ( |
279.4 | 311.96 | 293.5–332.8 | 910.31 | 27.23 | 4 (1.5%) |
Distribution of urinary iodine concentrations (
As age increased, students’ height, weight, BSA, and thyroid volume also increased as expected. However, the student group at the age of 19 or older showed smaller height, weight, and BSA, but larger thyroid volume than the student group at the age of 18 (Table
Height, weight, and thyroid volume according to age.
Age | Height (cm) | Weight (Kg) | BSA (m2) | Thyroid volume |
---|---|---|---|---|
≤13 ( |
152.7 ± 6.72 | 40.7 ± 6.31 | 1.31 ± 0.126 | 3.09 ± 0.86 |
14 ( |
153.1 ± 5.83 | 44.8 ± 7.11 | 1.38 ± 0.121 | 3.78 ± 1.12 |
15 ( |
157.00 ± 5.99 | 48.4 ± 5.83 | 1.45 ± 0.117 | 3.94 ± 1.24 |
16 ( |
157.30 ± 5.76 | 49.5 ± 6.00 | 1.47 ± 0.106 | 3.77 ± 1.20 |
17 ( |
159.50 ± 4.95 | 50.5 ± 3.53 | 1.50 ± 0.076 | 4.55 ± 1.02 |
18 ( |
160.75 ± 5.06 | 53.8 ± 4.79 | 1.55 ± 0.067 | 3.56 ± 1.16 |
≥19 ( |
156.75 ± 4.03 | 49.5 ± 5.45 | 1.47 ± 0.86 | 4.35 ± 0.65 |
For the first question, 56.8% of the students answered that they have heard about the problems associated with iodine deficiency. Although 62.3% of students answered that they can list some problems (disorders) resulting from iodine deficiency, most students (70.5%) chose goiter as the only problem (Figure
Problems list that the students chose as a result of iodine deficiency.
Routes of getting information about iodine deficiency disorders and prevention of them.
Preventing methods of iodine deficiency with the students listed.
Using status of iodized salt (a) and the reasons of not using iodized salt (b).
There was no significant difference in urinary iodine levels, height, and weight between the iodized salt using group and nonusing group. However, the thyroid volume was larger in the latter (
Urinary iodine and thyroid volume according to consuming ionized salt.
Using iodized salt | Nonusing iodized salt |
|
|
---|---|---|---|
Urinary iodine | 394.71 ± 237.65 | 336.88 ± 172.35 | 0.099 |
Thyroid volume | 3.71 ± 1.03 | 4.35 ± 2.47 | 0.032 |
Height (cm) | 155.15 ± 6.13 | 156.35 ± 6.27 | 0.277 |
Weight (Kg) | 46.61 ± 6.49 | 47.69 ± 7.33 | 0.384 |
WHO defined iodine deficiency as “the single most important preventable cause of brain damage” worldwide [
The Philippines also turns out to be one of the countries with adequate iodine nutrition according to the current study, which demonstrated that the median urinary iodine level was 355.3
According to the WHO criteria, the median UI level (355.3
In this study, we presented questionnaires to the subjects to evaluate an awareness status of iodine deficiency. Surprisingly, despite the fact that iodine deficiency status was improved, many students did not have proper knowledge regarding the condition. Most importantly, a majority of the students were unable to list the problems associated with iodine deficiency except goiter. Only 4.8% of students listed miscarriage/stillbirth and 17.1% listed retarded development of children as such problems (Figure
In 1993, the WHO reaffirmed salt iodization as the central strategy to eliminate iodine deficiency [
There was no difference in the urinary iodine levels between the group of students who answered “no” and that of students who answered “yes” to the question on whether to buy iodized salt. However, it is intriguing that the thyroid volumes were larger in the “no” group than in the “yes” group with a statistical significance (Table
Our current study revealed that only 4% of high school students are iodine deficient in Tuguegarao, the Philippines, indicating that iodine deficiency in this age group has been nearly overcome by efforts of the Philippines government and the WHO ICCIDD. Moreover, the Philippines Food and Drug Administration ordered salt manufacturers to increase the mandatory salt iodine content from 20 ppm to 30 ppm in 2013. For this reason, even further improvement is expected [
In order to completely eliminate iodine deficiency, the future strategy should be more focused on vulnerable groups through more effective education. According to our survey, most students gathered information regarding iodine deficiency in school and through media (Figure
Our study is conducted in only one area of the Philippines; however, it could be helpful for many countries with a similar iodine status around the world to establish their own public health strategies to eliminate iodine deficiency. Several studies suggested that public education programs are needed to improve iodine status [
The authors declare that there is no conflict of interests regarding the publication of this paper.
Bu Kyung Kim and Jee-Yeong Jeong contributed equally.
The authors would like to thank Dr. Amir Makhmudov and Dr. Kathleen Caldwell of USCDC for their helpful suggestions and for providing the Standard Reference Materials for the UI analysis. This work was supported in part by a grant from Kosin University College of Medicine to Young Sik Choi and by KNRF Grant 2012R1A1A2042188 to Jee-Yeong Jeong.