|Year : 2019 | Volume
| Issue : 3 | Page : 108-112
Iodine nutrition status in Graves' disease: A single-center study from Bangladesh
Md Abu Jar Gaffar1, A B. M. Kamrul-Hasan2, Afsar Ahammed3, Muhammad Abul Hasanat4, Md Fariduddin4
1 Department of Physiology, Naogaon Medical College, Naogaon, Bangladesh
2 Department of Endocrinology, Mymensingh Medical College Hospital, Mymensingh, Bangladesh
3 Department of Physiotherapy, National Institute of Traumatology and Orthopedic Rehabilitation, Dhaka, Bangladesh
4 Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh
|Date of Submission||16-Jul-2019|
|Date of Acceptance||23-Oct-2019|
|Date of Web Publication||18-Nov-2019|
Dr. A B. M. Kamrul-Hasan
Department of Endocrinology, Mymensingh Medical College Hospital, Mymensingh 2200
Source of Support: None, Conflict of Interest: None
Context: An increase in occurrence of Graves' disease (GD) has been reported in many countries after the introduction of the salt iodization program.
Aims: To observe iodine nutrition status in GD.
Settings and Design: Cross-sectional observational study conducted in the Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh from May 2013 to September 2014.
Methods and Material: This study included 140 GD patients (55 newly detected, 85 already under treatment). Urinary iodine concentration (UIC) was measured in spot urine sample following wet digestion method. The iodine nutrition status was categorized according to the internationally recommended cutoffs of UIC (excessive: ≥300 μg/L, more than optimal: 200-299 μg/L, optimal: 100-199 μg/L, deficiency: <100 μg/L).
Results: The median UIC in subjects with Graves' disease was 96.69 μg/L. 21.2% of the study subjects had iodine status to be considered as more than optimal or excessive, 25.7% had optimal iodine level, and more than half (51.4%) had iodine deficiency. The mean UIC were similar in newly diagnosed and treated groups, and among subjects with different thyroid functional status. UIC did not differ among male and female subjects and among subjects from different socioeconomic groups. UIC showed no correlations with age, socioeconomic condition, the family history of thyroid disease, TSH, FT4, and thyroid function status of the study participants.
Conclusions: Effective monitoring of salt iodization program is needed to prevent iodine-excess related increase in the prevalence of Graves' disease.
Keywords: Graves' disease, hyperthyroidism, iodine nutrition status
|How to cite this article:|
Gaffar MA, Kamrul-Hasan A B, Ahammed A, Hasanat MA, Fariduddin M. Iodine nutrition status in Graves' disease: A single-center study from Bangladesh. Thyroid Res Pract 2019;16:108-12
|How to cite this URL:|
Gaffar MA, Kamrul-Hasan A B, Ahammed A, Hasanat MA, Fariduddin M. Iodine nutrition status in Graves' disease: A single-center study from Bangladesh. Thyroid Res Pract [serial online] 2019 [cited 2019 Dec 12];16:108-12. Available from: http://www.thetrp.net/text.asp?2019/16/3/108/271154
| Introduction|| |
A few decades ago, iodine deficiency was prevalent in most parts of the world and was the leading cause of acquired hypothyroidism worldwide. The universal salt iodization (USI) program to achieve the elimination of iodine deficiency disorders has successfully eliminated this problem in many countries including Bangladesh. On the contrary, an increase in thyroid disorders (thyroid autoimmunity, hypo- and hyperthyroidism) has been reported in many countries even after a small increase in the iodine level after the introduction of the salt iodization program.,,,,,,,, To date, no data are available on the thyroid function status, particularly in the context of the expression of Graves' disease, after the introduction of the salt iodization program in Bangladesh. This study was conducted to know the iodine nutrition status of patients with Graves' disease in this area.
| Subjects and Methods|| |
This cross-sectional, observational study was conducted in the Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh, from May 2013 to September 2014. All patients with a diagnosis of Graves' disease according to thyroid function tests, thyroid ultrasonography, and thyroid scan reports attending the Endocrinology inpatient and outpatient departments of BSMMU within the study period were included in the sample after considering the exclusion criteria. Thus, 140 cases of Graves' disease (55 new cases and 85 previously diagnosed and getting antithyroid drug) irrespective of age and sex were enrolled in this study by nonprobability purposive sampling technique. Prior to the commencement of this study, the research protocol was approved by the Institutional Review Board. All patients included in this study were informed about the nature of the study and agreed to participate voluntarily in this study. Informed written consent from the patients was obtained. Pregnant and lactating women, patients taking drugs that may interfere thyroid function (e.g., amiodarone and lithium), patients with current or recent severe acute illness, and patients with other chronic autoimmune diseases or chronic debilitating conditions were excluded from the study. All patients were interviewed by a structured questionnaire. Five-milliliter spot urine sample was collected from each patient in screw-capped de-iodinized plastic cups and transferred to tightly sealed de-iodinized tubes and preserved under −20°C in a refrigerator till analysis in the Department of Designated Reference Institute for Chemical Measurements of Bangladesh Council of Scientific and Industrial Research, Dhaka.
Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured by chemiluminescent sequential immunometric assay with the IMMULITE 2000 system analyzers (Siemens Healthcare Diagnostics Inc., 511 Benedict Avenue, Tarrytown, NY 10591-5005, USA) in the Department of Microbiology, BSMMU. The laboratory reference for nonpregnant adults for TSH and FT4 was 0.4–4.0 μIU/mL and 0.8–1.8 ng/dL, respectively. The urinary iodine concentration (UIC) was estimated by using the wet digestion method described by Dunn et al. with modification of Sandell and Kolthoff., Cross-checking was done on a random sample basis to find any major variability of the results of UIC among the assay runs. The iodine nutrition status was categorized according to urinary iodine (UI) levels according to the WHO/UNICEF/International Council for Control of Iodine Deficiency Disorders (ICCIDD)-recommended cutoffs (excessive: ≥300 μg/L, more than optimal: 200–299 μg/L, optimal: 100–199 μg/L, and deficient: <100 μg/L).
Data were analyzed using IBM SPSS Statistics for Windows, version 23.0 (IBM Corp., Armonk, NY, USA) software. The categorical variables were presented as percentages and measurable variables as mean ± standard deviation or median. Student's t-test, Chi-square test, and one-way ANOVA test were performed for comparing the variables between different groups as appropriate. Pearson's and Spearman's correlation tests were used to observe the correlation of UIC with other variables. P ≤ 0.05 was considered statistically significant.
| Results|| |
In the present study, 140 patients of Graves' disease were investigated to observe the iodine nutrition status, of which 55 were newly detected and 85 were under treatment.
The demographic and thyroid profiles of the studied patients are summarized in [Table 1]. Their mean age was 34 ± 10 years, male:female ratio was 34.3:65.7, and 16% of them had a family history of thyroid disease. Most (87.9%) of them where hyperthyroid. All the patients (100%) were taking iodized salt.
|Table 1: Demographic and thyroid profiles of the studied participants (n=140)|
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The mean and median UIC of the study patients are summarized in [Table 2]. The overall mean and median UIC were 131.14 (±10.50) and 96.69 μg/L, respectively. The mean UIC was similar irrespective of the treatment status and thyroid function status.
[Table 3] summarizes the UI status considering the recommended cutoffs; 51.4% of the study patients were iodine deficient, 25.7% had optimal iodine status, and 22.9% of the study patients had more than optimal or excessive iodine. Iodine status was similar among male and female patients, among untreated and treated patients, and among patients of different socioeconomic status.
Comparison of UIC among different subgroups of the study patients is shown in [Table 4]; there was no statistical difference of UIC among male and female patients. UIC was also similar in patients with different socioeconomic statuses.
|Table 4: Urinary iodine status in different gender and socioeconomic status of the study patients|
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Correlations of UI level with other variables are summarized in [Table 5]. Age, socioeconomic status, presence of the family history of thyroid disease, thyroid functional status, TSH, and FT4 did not have any significant correlations with UIC.
|Table 5: Correlations of urinary iodine level with other variables (Pearson's or Spearman's)|
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| Discussion|| |
In the present study, the median UIC in patients with Graves' disease was 96.69 μg/L. It was clearly observed that 21.2% of the patients suffering from Graves' disease had iodine status to be considered as more than sufficient, 25.7% had optimal iodine level, and more than half (51.4%) were deficient with iodine nutrition as judged on the basis of the recommended cutoff values. The mean and median values of UIC were similar in the treated and untreated groups and among patients with different thyroid functional statuses. Iodine nutrition status did not differ among male and female patients and among different socioeconomic groups. UIC showed no correlations with age, socioeconomic condition, family history of thyroid disease, TSH, FT4, and thyroid function status of the study participants.
Iodine is an essential requirement for thyroid hormone synthesis and in adults, the recommended daily iodine intake is 150 μg. Nutritional iodine status is an important factor associated with thyroid dysfunction and thyroid autoimmunity. The introduction of iodine fortification of salt and the appearance of various iodine fortifications in food greatly improved the iodine nutritional status and has almost eliminated endemic goiter in many countries worldwide including Bangladesh. Iodine excess which is currently a more frequent occurrence than iodine deficiency as reflected by the WHO data demonstrates that over thirty countries worldwide currently have more-than-adequate or excessive iodine intake. Iodine excess has been found to be associated with thyroid dysfunctions and to induce or precipitate thyroid autoimmunity.,,, Alongside, a marked increment of occurrence of overt Graves' disease has been observed in several countries after the commencement of salt iodination program.,,, Iodine intake may set the course in patients with Graves' disease because of a slight increase in dietary iodine results in frank hyperthyroidism patients with latent Graves' disease and a decreased efficacy of antithyroid treatment. In addition, in iodine-deficient areas, the response to antithyroid agents is better and lower doses are required for hormone control.
The only epidemiological criterion available for assessing the iodine nutrition status is based on median UI level, in which median UI level >100 μg/L is considered as adequate. In light of that, the present study showed median UI values in newly diagnosed, treated, and overall groups to be 104.35, 93.11, and 96.69 μg/L, respectively. The Government of Bangladesh passed a law making it mandatory for all edible salt to be iodized in 1989. Fortification of salt with iodine was initiated in 1990 and the success of the program was revealed by a UNICEF survey in 1999, which indicated that the proportion of households consuming iodized salt had risen to 71%. Another survey in 2004–2005 found normal median UIC in rural women and children (123 μg/L and 141 μg/L, respectively). In the current study, 100% of the participants took iodized packet salts, so it is expected to find median UI values above or near to the optimum level. However, here, only the newly diagnosed patients had median UI value >100 μg/L but not the treated group or when all patients considered together, although mean values for each group exceeded 100 μg/L. When iodine nutrition status was assessed under recommended cutoff values, it was observed that 25.7% of the patients had optimal iodine nutrition status and 22.9% had more than optimal or excess iodine. We have no previous data for the iodine nutrition status of the patients with Graves' disease. In Bangladesh, the prevalence of Graves' disease in the iodine-deficiency era and at present is also unknown. Hence, it is not possible to comment on whether improving iodine nutrition status with USI program had influences on the changing prevalence of Graves' disease in this area. Moreover, it is important to reiterate the benefits of eradicating iodine deficiency-related thyroid diseases and mental retardation that affected a large population across the globe in the past. We must be aware of the adequate monitoring of the salt iodization keeping in mind the possible adverse outcomes of excess iodization.
Our study had several limitations. As this is a tertiary hospital-based study, observation may not represent the iodine nutrition status of Graves' disease of the whole community. No healthy control group was taken which might have diluted the importance of comparisons and observations. The iodine content of the patients' household table salt was also not measured.
| Conclusion|| |
This study observed that although the median UIC (96.69 μg/L) was close to the level of optimum iodine nutrition status, around half (51.1%) of the patients with Graves' disease attending a tertiary hospital of Bangladesh had iodine deficiency and 22.9% had more than optimal or excessive iodine. The causal relationship of iodine nutrition status with Graves' disease, particularly in our context, could not be explored due to lack of previous data. Therefore, further large-scale, controlled studies relating iodine supplementation, iodine nutrition status, and Graves' disease are required to know the interaction of salt iodization and Graves' disease in Bangladesh.
Financial support and sponsorship
The study was funded by the National Institute of Population Research Training, Bangladesh.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]