|Ahead of print publication
Thyroid disorders in arsenic prevalent area in Bangladesh
Mohammad Moin Shahid1, Khadiza Begum2, Kaniz Rahman3, Hosnea Ara4, Sharmin Ferdousi5, Richmond Ronald Gomes2
1 Department of Endocrinology, Ad-din Women's Medical College, Mogbazar, Dhaka, Bangladesh
2 Department of Internal Medicine, Ad-din Women's Medical College, Mogbazar, Dhaka, Bangladesh
3 Department of Dermatology, Ad-din Women's Medical College, Mogbazar, Dhaka, Bangladesh
4 Department of Psychiatry, Ad-din Women's Medical College, Mogbazar, Dhaka, Bangladesh
5 Department of Department of Pathology, Dr. Sirajul Islam Medical College, Mogbazar, Dhaka, Bangladesh
|Date of Submission||27-Mar-2021|
|Date of Acceptance||06-Apr-2021|
|Date of Web Publication||04-Sep-2021|
Mohammad Moin Shahid,
Department of Endocrinology, Ad-din Women's Medical College, Mogbazar, Dhaka
Source of Support: None, Conflict of Interest: None
Background and Objectives: Due to geographical position and geological nature, Bangladesh (BD) has been the worst affected country in the world by arsenic contamination. The aim of this study was to highlight the association of chronic arsenic intoxication with thyroid disorders (TDs).
Materials and Methods: This cross-sectional study was conducted from March 2019 to February 2020 at Ad-din Women's Medical College and Hospital. One thousand one hundred and thirty-seven patients were randomly selected, who visited the outpatient departments of medicine faculty with thyroid-stimulating hormone test report. Rest of the thyroid function tests were done if required. Considering the arsenic level in irrigation and drinking water, 64 districts of BD were divided into two regions “arsenic prevalent area” and “less arsenic prevalent area” and patients hailing from those areas were divided as Group 1 and Group 2, respectively. All patients were subjected to history taking and physical examination. Chi-square test and one-way ANOVA test were used to compare the variables.
Results: Prevalence of TD were significantly higher in Group 1 (60.14%; P = 0.001) and so was the prevalence of goiter (19%;P = 0.021). Older (31.17 ± 9.81;P = 0.001) and female patients (94.92%;P = 0.001) were more prone to develop TD.
Conclusion: It will require more studies at larger scale for better understanding of the association of thyroid disorders with chronic arsenic intoxication.
Keywords: Arsenic intoxication, geography, geology, thyroid disorder
|How to cite this URL:|
Shahid MM, Begum K, Rahman K, Ara H, Ferdousi S, Gomes RR. Thyroid disorders in arsenic prevalent area in Bangladesh. Thyroid Res Pract [Epub ahead of print] [cited 2021 Dec 9]. Available from: https://www.thetrp.net/preprintarticle.asp?id=325592
| Background|| |
Bangladesh (BD) is a land of rivers. Most parts of BD are deltaic areas and flood plains. Due to geographical position and geological nature, the groundwater of BD is highly contaminated with arsenic (As)-in fact, the worst in the world.,, Arsenic has many harmful effects on the human body.,,, Thyroid disorder (TD) is one of the most common endocrine disorders in BD and researches have showed that arsenic has direct and indirect role in the development of TD. Despite being the most arsenic-contaminated country in the world, BD do not have any study co-relating arsenic and TD. The aim of this study to highlight the effect of chronic arsenic intoxication on TD.
| Materials and Methods|| |
This is a cross-sectional study which was conducted from March 2019 to February 2020 at Ad-din Women's Medical College a Tertiary Care Hospital in Dhaka, BD. One thousand one hundred and thirty-seven patients were randomly selected, who visited the outpatient departments of medicine faculty with thyroid function test report– thyroid-stimulating hormone (TSH). Free triiodothyronine (FT3)/total triiodothyronine (TT3), free thyroxine (FT4)/total thyroxine (TT4), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) levels were checked when required. Thyroid status was classified according to TSH value– euthyroidism, subclinical hypothyroidism (SCH), hypothyroidism (HypoTh), hyperthyroidism (HyperTh), and subclinical hyperthyroidism (SCHy). According to the American Thyroid Association (ATA) and hospital laboratory reference value; euthyroidism, when TSH level is 0.35-–5.5 μIU/mL (if pregnant then 0.35–3.9 μIU/mL); SCH, when TSH is 5.6–9.9 μIU/mL (during pregnancy-4.0–9.9 μIU/mL); HypoTh, when TSH is ≥10 μIU/m. If TSH is <0.35 μIU/mL but FT4/TT3, FT3/TT4 is above range then the diagnosis is HyperTh, if FT4/TT3, FT3/TT4 levels are within range then the diagnosis is SCHy. Serum level of TgAb ≥ 4.11 IU/mL and TPOAb ≥ 5.61 IU/mL were considered as cut off values for presence of thyroid autoantibodies.
- All patients reported to the outpatient departments of medicine faculty with thyroid function test.
- Patients with iatrogenic TD– drug-induced/surgery/radio ablation
- Critically ill patient.
According to Situation Analysis of Arsenic Mitigation, 2009 report (conducted by Department of Public Health Engineering, Government of Peoples Republic Of BD and Japan International Cooperation Agency), 31 districts of BD – Dhaka (except city corporation area), Narayanganj, Narsingdi, Munsiganj, Shariatpur, Madaripur, Faridpur, Goplaganj, Brahmonbaria, Comilla, Noakhali, Lakshmipur, Chadpur, Feni, Barisal, Jhalokathi, Jamalpur, Kishoreganj, Manikganj, Netrokona, Sunamganj, Shylet, Sirajganj, Jessore, Bogura, Meherpur, Chuadanga, Tangail, Habiganj, Pabna, and Rajbari were grouped as “arsenic prevalent area” where (whole district or part of the district) >40% of irrigation and drinking water well water's arsenic level was >0.05 mg/dl. Moreover, the rest 33 districts were labeled as “less arsenic prevalent area”. Patients who reside at arsenic prevalent areas or used to live in those areas at least for 10 years or their parents are from areas were grouped as Group 1 and others were in Group 2. Seven hundred patients belonged to Group 1 and rest, 421 patients belonged to Group 2. Following informed written consent, all patients were subjected to history taking and physical examinations. TSH, FT4, FT3, TT4, TT3, TPOAb, TgAb were analyzed by using immunoassay with IMMULITE 1000(Siemens, Germany) immunoassay analyzer . Statistical analysis was done using SPSS 23 (IBM, United States of America) software.
| Results|| |
The mean age of patients with thyroid disorder is significantly higher than the patients without thyroid disorder and so is the number of female patients with thyroid disorder comparing to the male patients. Presence of TD and goiter are significantly higher among people from arsenic prevalent areas (Group 1).
| Discussion|| |
Arsenic contamination of groundwater in BD was first reported in 1992. Arsenic is highly toxic which can lead to a wide range of health problems in humans. Various skin lesions (e.g., hyperpigmentation, hyperkeratosis, and hypopigmentation) blackfoot disease, peripheral neuropathy, encephalopathy, hepatomegaly, cirrhosis, altered heme metabolism, bone marrow depression, diabetes, proximal renal tubule degeneration, renal papillary, and cortical necrosis as well as various malignancies have been reported due to chronic arsenic exposure.,,, Although arsenic has been reported as an endocrine disruptor in some studies its role in human thyroid dysfunction is not clear yet,,, Davey et al. reported that in model animal system arsenic alters thyroid hormone receptors mediated gene regulation and suggested strong possibility that it can also dysregulate thyroid function in the human body in the same manner. We have come to a hypothesis that chronic arsenic intoxication causes selenium (Se) deficiency in the human body which results in TDs. Arsenic is 47th and selenium 70th in abundance of the 88 naturally occurring elements. Although arsenic is highly toxic for the human body selenium is an essential trace element. Selenoproteins have important anti-inflammatory and antioxidant activities in the human body. Low selenium status has been associated with increased risk of developing Keshan disease, poor immune function, cognitive decline, mood disorder, infertility, and autoimmune TDs.,, Unfortunately, selenium level in the soil of BD is very low. Geological nature (alluvial origin and acidic soil) and meteorological phenomenon (heavy rainfall and flood) of BD are the possible reasons behind this., Moreover, for the same reasons as well as the geographical position, the soil of BD is highly contaminated with arsenic.,, As a result the plant origin foods contain high level of arsenic but low level of selenium which is the main source of food for BD i people., Although animal proteins are considered as good source of selenium and fish is the main protein source for BD i people Al-Rmalli et al. reported high level of arsenic in different species of fish in BD. Due to socioeconomic condition many Bangladeshi people do not get adequate protein according to their daily needs. Usually, arsenic and selenium have an antagonistic relationship between them.,, Arsenic toxicity is enhanced if the selenium level is also very high. But at lower concentration of Selenium, it decreases Arsenic toxicity by creating As-Se compound [(GS3)2AsSe] which is excreted through bile. Since many Bangladeshi people are already Se deficient and exposed to chronic arsenic toxicity, the effort of Se to minimize the toxicity can further decrease the Selenium level in the human body. The thyroid contains the highest concentration of selenium in the human body. There are several selenoprotiens which are expressed in thyrocytes which are essential for thyroid homeostasis, for example, deiodinases, glutathione peroxidases. Moreover chronic deficiency of Se is an important cause of developing autoimmune TDs. Stojsavljević et al. have reported high level of As and low level of Se in thyroid tissue of patients with autoimmune thyroid disease (AITD) (Hashimoto's thyroiditis).
It is known that TDs are more common as age progresses and females are more affected than males., The findings of our study in these regards were evidently indifferent [Table 1]. This study showed that the prevalence of TDs is significantly higher in arsenic prevalent areas [Table 2]. We have also noticed that TDs are more prevalent in the areas which are adjacent to the main rivers of BD – the Padma, the Meghna, the Jamuna, and the Brahmaputra [Table 3]. Geology of the river adjacent areas is mostly alluvial in nature which characteristically contains high level of arsenic.,, According to Sharpless et al., nontoxic exposure to arsenic does not have any effect on the thyroid gland but arsenic can act as a goitrogen if there is chronic toxic exposure. Besides that Kishosha et al. have reported that selenium deficiency is also associated with the development of goiter. In our study, we have also found significantly high prevalence of goiter in arsenic prevalent areas [Table 2]. Although arsenic toxicity and selenium deficiency, both are related to high titer of thyroid autoantibodies, therefore AITDs but we did not find any significant difference in prevalence of thyroid autoantibodies (TPOAb and TgAb) between Group 1 and 2.,, Genetic transmission is one of the important characters of AITD.,, However, in this there was no significant difference of positive family history of TD between two groups.
|Table 2: comparison between arsenic prevalent area (Group 1) and less arsenic prevalent area (Group 2)|
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Due to our limited resources, we could not evaluate the arsenic and selenium status of the patients. Many patients could not mention any family history related to TD as they and their family were not familiar with these disorders. More than half of the total cases did not check their thyroid antibody status as advised.
It is inevitable that BD will have to deal with arsenic contamination as always. Extensive studies need to be conducted to learn more about the relationship between chronic arsenic exposure and TDs so that we can find a way out of this condition.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]