Iodine nutritional status of children in North East India
http://www.100md.com
《美国医学杂志》
1 Department of Physiology, University College of Science and Technology, University of Calcutta, Kolkata, India
2 Department of Zoology, D.M. College of Science, Manipur, India
3 Department of Pharmaceutical Technology,Jadavpur University, Kolkata, India
Abstract
Objective. To assess the iodine nutritional status of school children in selected areas of Imphal West District of Manipur where endemic goitre and associated iodine deficiency disorders (IDD) are prevalent in the post-salt iodization period. Methods. A total of 961 school children in the age group 6-12 yrs of both sexes were clinically examined for goiter from three study areas- one from rural block and two from urban areas. One hundred twenty urine samples were analysed for iodine and thiocyanate respectively. One hundred and five edible salt samples were also collected from the households to evaluate the iodine content. Drinking water samples from different sources were collected and iodine level was analysed to study the bioavailability of iodine in the region. Results. The total goiter rate was 34.96% (Grade 1- 32.15%; Grade 2- 2.81%) showing that IDD is a severe public health problem. The median urinary iodine levels in the studied areas were in the ranges from 12.5-17.5 μg/dl indicating no biochemical iodine deficiency in the region. Mean urinary thiocyanate level was 0.839±0.33 mg/dl showing that the people consume sufficient foods containing thiocyanate precursors. About 82% salt samples had iodine level more than 30 ppm and the iodine content in salt samples less than 15 ppm was only about 3% indicating the salt samples at house hold contain adequate iodine. Conclusion. Iodine content in drinking water samples ranged from 1.8-2.6 μg/l showing that the studied region is environmentally iodine deficient. Inspite of the consumption of adequate iodine, the existing goiter prevalence among school children during post salt iodization phase ensures that environmental factors other than iodine deficiency may have the possible role in the persistence of endemic goiter in the population. The role of thiocyanate in this regard may not be ruled out.
Keywords: Endemic goiter; Iodine nutrition; Dietary goitrogen; Thiocyanate
Iodine is an important micronutrient required for human nutrition. Lack of iodine in the diet leads to visible and invisible spectrum of health consequences collectively called iodine deficiency disorders (IDD). IDD are now considered as major public health problem all over the world including India. Its major manifestations are goitre (enlargement of thyroid gland than normal), mental defects, deaf mutism, stillbirth and miscarriages, weakness and paralysis of muscles as well as lesser degree of physical and mental dysfunction.[1] Iodine deficiency also affects the socio-economic development of a community.[2] In India, a nation-wide goitre survey revealed that out of 283 studied districts of 29 states and 4 union territoies, 235 have prevalence of endemic goitre[3]. In the post-salt iodisation phase endemic goitre has been reported from many new areas.[4],[5],[6]
Manipur is located in the foothills of the Himalayas. Due to its geographical location, the entire state is in the classical goitre endemic belt of India.[7] The total area of the Imphal West District is about 558 sq. km. and the population is about 4, 39, 532 (2001 Census Report). Reports on the status of iodine nutrition of the people in this most thickly populated district are not adequately available. According to survey reports conducted by IDD cell, Govt. of Manipur in 1992 & 1996, the goitre prevalence in Manipur was 21.1% and 13.0% respectively. Universal salt iodization programme was enforced in the state during the late eighties. Reports on endemic goitre and iodine nutritional status are not available from the Imphal West District of Manipur. Thus, the present work was undertaken to study the prevalence of goitre, state of iodine nutrition of the population, distribution of iodine through iodized salt, bioavailability of iodine, consumption pattern of common goitrogenic foods that generally interfere with iodine nutrition etc. in certain randomly selected areas of Imphal West District.
Materials and methods
Selection of Study Area : Imphal West is a centrally located valley district of Manipur. Four districts viz, Senapati, Imphal East, Bishnupur and Thoubal surround it. This valley district is a high level flood plain with an elevation of about 760 meters above the mean sea level. A number of occasional hills and mounds rise above the flat surface and these include Langol ching, Langjing ching, and Chinga. It has 11 towns and 2 rural Community Development Blocks. In the present study 3 localities - 1 from rural Block and 2 from urban areas were selected by random purposive sampling method [8].
Selection of Population : As per recommendation of WHO/UNICEF/ICCIDD [9], the school children in the age group 6-12 yrs from both sexes were selected. To get the target population in selected locality, one primary school, one Junior High School and one High School were selected.
Clinical Goitre Survey : School children were clinically examined for the enlargement of thyroid (goitre) by palpation method endorsed by WHO/UNICEF/ICCIDD (Grade 0: no goitre; Grade 1: thyroid palpable but not visible; and Grade 2: thyroid visible with the neck in normal position)[10]. The age of the students was recorded from the school register and was rounded off to the nearest whole number.
Iodine in Urine : One hundred and twenty urine samples were randomly collected from the children of the studied schools (40 samples from each area) in wide mouth screw capped plastic bottles. A drop of toluene was added to each urine sample to inhibit bacterial growth and to minimize bad odour. The samples were brought to the laboratory and kept at 4 osub C till analyzed. Iodine in urine was then determined by the arsenite method following dry ashing in presence of potassium carbonate[11] maintaining Internal Quality Control having a known concentration range of iodine content with each batch of test samples.
Thiocyanate in Urine : Thiocyanate content in the urine was measured following the method of Aldridge[12] and modified by Michajlovskij and Langer[13]. The people of the studied areas were also interviewed regarding the consumption of cyanogenic foods for the identification of thiocyanate load.
Iodine in Salt and Water : To monitor the iodine content of salt samples available in the area, 35 marked air-tight plastic containers were distributed[14] at random to the students of the studied schools and they were asked to bring edible salt samples from their households the next day. The salt samples were kept at room temperature in the laboratory and iodine content was measured within a week by iodometric titration method[15].
The sources of dietary iodine are water, food and the iodised salt available in the studied area. Iodine content in water of a region truly reflects the bioavailability of iodine. Fifteen drinking water samples were collected at random (5 samples from each area) in screw capped plastic bottles. The samples were brought to the laboratory, kept at 4 osub C till analyzed. The iodine level was then determined by the method of Karmarkar et al[11].
For the analysis of data mean, median and standard deviation have been used.
Results
Goitre Prevalence : In all 961 school children from 3 study areas were clinically examined for goiter and the total goitre rate was 34.96%. Area wise goitre prevalences are given in table1. A progressive increase in goitre prevalence was found from the age group of 6 years till the age of 8 years followed by a short decline from the age of 9 to 10 yrs and then again increased upto 12 years. Most of the goitre were of Grade 1 (32.15%) but Grade 2 was also seen in the selected population. Age specific goitre prevalence is shown in table2.
Iodine in Urine : Pattern of urinary iodine excretion of the studied population from the 3 areas of Imphal West is shown in table3. In all, 120 urine samples were collected taking 40 from each area. 25% of total samples had iodine excretion level below 10 μg/dl and 6.7% had iodine level below 5 μg/dl while the median urinary iodine (MUI) was 14.75 μg/dl.
Thiocyanate in Urine : The urinary thiocyanate level is also shown in table3. The mean urinary thiocyanate level was 0.839 ± 0.33 mg/dl indicating that the entire studied population was exposed to thiocyanate load.
Iodine in Salt and Drinking Water : Iodine content in edible salt fortified with iodine was measured and it was found that all the salt samples tested had iodine. 2.9% salt samples had iodine level below 15 ppm, 15.2% salt samples had iodine level above 15 ppm but below 30 ppm and 81.9% salt samples had iodine level more than or equal to 30 ppm table4.
Iodine content in drinking water of the studied region was determined from different water sources in the localities and the mean iodine value was 2.3 ± 0.4 μg/l table4.
Discussion
The most widely accepted marker to evaluate the severity of IDD in a region is the prevalence of endemic goitre in school children. On the basis of its prevalence, WHO/UNICEF/ICCIDD[14] recommended the criteria to understand the severity of IDD as a public health problem in a region. According to these criteria, a prevalence rate of 5.0 - 19.9% is considered as mild; 20.0 - 29.9% as moderate and a prevalence rate of above 30% is considered as a severe public health problem.
Goitre is prevalent at endemic level in all study areas even years after salt iodization program among children and this was evidenced by total goiter rate of 34.96% (Grade 1: 32.15%; Grade 2: 2.81%) in the studied areas indicating that IDD is still a severe public health problem in this region.
The present findings of the urinary iodine excretion level revealed that the studied population had no biochemical iodine deficiency, which has been shown by median urinary iodine of 14.75 μg/dl, and 6.7% population had iodine level below 5 μg/dl. It may be mentioned that a median urinary iodine concentration of 10μg/dl and not more that 20% of the samples are below 5μg/dl in an area indicates no iodine deficiency.[14]
WHO/UNICEF/ICCIDD further recommends that 90% of the household salts should get iodized at the recommended level of 15ppm[16] but the study shows that more than 95% of the households are consuming salts at adequate level.
An indication in the iodine content of the soil can be given by the local drinking water concentration.[1] Iodine content in drinking water indicates that study region is environmentally iodine deficient or the soil is poor in iodine according to Zeltser et al.[17]
The consumption of cyanogenic plant foods was also evident from the urinary excretion of thiocyanate (SCN). In India, large number of cyanogenic plants (SCN precursors) are used as common vegetables and IDD thus persists in many regions inspite of recommended iodine intake.[5], [18],[19] Indian cyanogenic plant foods that are used as common vegetables have potent anti-thyroid activity and supplementation of extra iodine even fails to counteract their effect.[20] In a recent country wide study conducted by Marwaha et al (2003) reported that thiocyanate appers to play an important role in goitre formation especially among poor children in India in post iodisation phase [21]. It has been mentioned that mean value obtained from non-endemic population was 0.504 ± 0.197 mg/dl. The people of Manipur not only consume the common cyanogenic plant foods as vegetables but they also consume almost regularly bamboo shoot as pickle and sometimes as food by poor people containing large amount of thiocyanate precursors namely, cyanogenic glucosides, thioglucosides and thiocyanate. In our present study, the mean urinary thiocyanate value was 0.839 ± 0.33 mg/dl. So, the involvement of thiocyanate or thiocyanate precursors present in food consumed by the people of the region may not be ruled out.
The study, therefore, indicates that the presence of goitrogenic/anti-thyroidal substances may have the possible roles for the persistence of endemic goiter in this region and their action may not be antagonized by iodine supplemented at present level.
References
1. Hetzel BS. An overview of the prevention and control of iodine deficiency disorders. In. Hetzel BS, Dunn JT, Stanbury JB, editors. The Prevention and Control of Iodine Deficiency Disorders ; Elsevier, Amsterdam, 1987: p. 7-31.
2. Levin HM. Economic dimensions of iodine deficiency disorders. In Hetzel BS, Dunn JT and Stanbury JB, editors. The Prevention and Control of Iodine Deficiency Disorders ; Elsevier, Amsterdam, 1987: 195-208.
3. National iodine deficiency disorders control program: National Health Program Series 5. Published by Department of Communication, National Institute of Health and Family Welfare, New Delhi, 2003: p 99.
4. Chandra AK, Ray I. Dietary supplies of iodine and thiocyanate in the etiology of endemic goiter in Tripura. Indian J Pediatrics 2001; 68: 399-404.
5. Kochupillai N. Neonatal hypothyroidism in India. Mount Sinai Journal of Medicine 1992; 59(2): 111-115.
6. Pandav CS, Malik A, Anand K, Pandav S, Karmarkar MG. Prevalence of iodine deficiency disorders among school children of the national capital territory of Delhi. ICCIDD, Regional office of South Asia and Pacific, New Delhi (1996).
7. WHO/SEARO. Iodine deficiency disorders in South East Asia, SEARO, Regional Health. New Delhi, 1985: p. 10.
8. Cochran WG. Sampling techniques, Edition 3, Wiley Eastern Limited, Calcutta (1977).
9. Dunn JT, Crutchfield HE, Gutckunst R, Dunn AD. Iodine deficiency disorders and urinary iodine levels. In. Methods of measuring iodine in urine. The Netherlands: ICCIDD/UNICEF/WHO 1993: 7-10.
10. WHO/UNICEF/ICCIDD. Indicators for assessing Iodine Deficiency Disorders and their control through salt iodization. WHO/NUT/94.6, 1994.
11. Karmarkar MG, Pandav CS, Krishnamachari KAVR. Principle and Procedure for Iodine Estimation . A laboratory manual, Indian Council of Medical Research, New Delhi, 1986.
12. Aldridge WN. The estimation of micro quantities of cyanide and thiocyanate. Analyst , London, 1945; 70: 474-475.
13. Michajlovskij N, Langer P. Studien uber Benziehungen Zwischen Rhodanbildung und Kropfbildender Eigenschaft Von Nahrungsmitteln. I: Gehalt einiger Nahrungs Mittel an praformierten Rhodanid. Z Physiol Chem 1958; 312: 26-30.
14. Indicators for Trackling Progress in IDD Elimination. In IDD Newsletter 1994; 10: 37-41.
15. Titration methods for salt iodine analysis. In Monitoring Universal salt iodization programme (Edition Sullivan KM, Houston E, Gorestein J, Cervinskas J). UNICEF/ ICCIDD/PAMM/WHO, 1995: p 11.
16. ICCIDD/UNICEF/WHO. Assessment of iodine deficiency disorders and monitoring their elimination, A guide for programme managers, Second edition, WHO/NHD/01.1, 2001.
17. Zeltser ME, Aldarkhanov BA, Berezhnaya IM, Spernasky GG, Bazarbekova RB, Nurbekova AA, Levina SA, Mandrovnaya NV, Aripova AA. Iodine deficiency and its clinical manifestation in Kazakhastan. IDD Newsletter 1992; 8 (1): 5-6.
18. Delange F, Thilly C,Bourdoux P, Hennart P, Courtois P, Ermans AM. Influence of dietary goitrogens during pregnancy in humans on thyroid function of the newborn. In. Delange F, Iteke FB, Ermans AM eds. Nutritional Factors Involved in The Goitrogenic Action of Cassava . IDRC-184e, Int Dev Res Cent, Ottawa, 1982; p. 40-50.
19. Chandra AK, Ray I. Evaluation of the effectiveness of salt iodization status in Tripura, northeast India. Indian J Med Res 2002; 115: 22-27.
20. Chandra AK, Mukhopadhyay S, Lahari D, Tripathy S. Goitrogenic content of cyanogenic plant foods of Indian origin and their anti-thyroidal activity in vitro. Indian J Med Res 2004; 119: 180-185.
21. Marwaha RK, Tandon N, Gupta N, Karak AK, Verma K, Kochupillai N. Residual goitre in the postiodization phase: iodine status, thiocyanate exposure and autoimmunity. Clin Endocrinol 2003; 59 (6): 672-681.(Chandra Amar K, Singh L H)
2 Department of Zoology, D.M. College of Science, Manipur, India
3 Department of Pharmaceutical Technology,Jadavpur University, Kolkata, India
Abstract
Objective. To assess the iodine nutritional status of school children in selected areas of Imphal West District of Manipur where endemic goitre and associated iodine deficiency disorders (IDD) are prevalent in the post-salt iodization period. Methods. A total of 961 school children in the age group 6-12 yrs of both sexes were clinically examined for goiter from three study areas- one from rural block and two from urban areas. One hundred twenty urine samples were analysed for iodine and thiocyanate respectively. One hundred and five edible salt samples were also collected from the households to evaluate the iodine content. Drinking water samples from different sources were collected and iodine level was analysed to study the bioavailability of iodine in the region. Results. The total goiter rate was 34.96% (Grade 1- 32.15%; Grade 2- 2.81%) showing that IDD is a severe public health problem. The median urinary iodine levels in the studied areas were in the ranges from 12.5-17.5 μg/dl indicating no biochemical iodine deficiency in the region. Mean urinary thiocyanate level was 0.839±0.33 mg/dl showing that the people consume sufficient foods containing thiocyanate precursors. About 82% salt samples had iodine level more than 30 ppm and the iodine content in salt samples less than 15 ppm was only about 3% indicating the salt samples at house hold contain adequate iodine. Conclusion. Iodine content in drinking water samples ranged from 1.8-2.6 μg/l showing that the studied region is environmentally iodine deficient. Inspite of the consumption of adequate iodine, the existing goiter prevalence among school children during post salt iodization phase ensures that environmental factors other than iodine deficiency may have the possible role in the persistence of endemic goiter in the population. The role of thiocyanate in this regard may not be ruled out.
Keywords: Endemic goiter; Iodine nutrition; Dietary goitrogen; Thiocyanate
Iodine is an important micronutrient required for human nutrition. Lack of iodine in the diet leads to visible and invisible spectrum of health consequences collectively called iodine deficiency disorders (IDD). IDD are now considered as major public health problem all over the world including India. Its major manifestations are goitre (enlargement of thyroid gland than normal), mental defects, deaf mutism, stillbirth and miscarriages, weakness and paralysis of muscles as well as lesser degree of physical and mental dysfunction.[1] Iodine deficiency also affects the socio-economic development of a community.[2] In India, a nation-wide goitre survey revealed that out of 283 studied districts of 29 states and 4 union territoies, 235 have prevalence of endemic goitre[3]. In the post-salt iodisation phase endemic goitre has been reported from many new areas.[4],[5],[6]
Manipur is located in the foothills of the Himalayas. Due to its geographical location, the entire state is in the classical goitre endemic belt of India.[7] The total area of the Imphal West District is about 558 sq. km. and the population is about 4, 39, 532 (2001 Census Report). Reports on the status of iodine nutrition of the people in this most thickly populated district are not adequately available. According to survey reports conducted by IDD cell, Govt. of Manipur in 1992 & 1996, the goitre prevalence in Manipur was 21.1% and 13.0% respectively. Universal salt iodization programme was enforced in the state during the late eighties. Reports on endemic goitre and iodine nutritional status are not available from the Imphal West District of Manipur. Thus, the present work was undertaken to study the prevalence of goitre, state of iodine nutrition of the population, distribution of iodine through iodized salt, bioavailability of iodine, consumption pattern of common goitrogenic foods that generally interfere with iodine nutrition etc. in certain randomly selected areas of Imphal West District.
Materials and methods
Selection of Study Area : Imphal West is a centrally located valley district of Manipur. Four districts viz, Senapati, Imphal East, Bishnupur and Thoubal surround it. This valley district is a high level flood plain with an elevation of about 760 meters above the mean sea level. A number of occasional hills and mounds rise above the flat surface and these include Langol ching, Langjing ching, and Chinga. It has 11 towns and 2 rural Community Development Blocks. In the present study 3 localities - 1 from rural Block and 2 from urban areas were selected by random purposive sampling method [8].
Selection of Population : As per recommendation of WHO/UNICEF/ICCIDD [9], the school children in the age group 6-12 yrs from both sexes were selected. To get the target population in selected locality, one primary school, one Junior High School and one High School were selected.
Clinical Goitre Survey : School children were clinically examined for the enlargement of thyroid (goitre) by palpation method endorsed by WHO/UNICEF/ICCIDD (Grade 0: no goitre; Grade 1: thyroid palpable but not visible; and Grade 2: thyroid visible with the neck in normal position)[10]. The age of the students was recorded from the school register and was rounded off to the nearest whole number.
Iodine in Urine : One hundred and twenty urine samples were randomly collected from the children of the studied schools (40 samples from each area) in wide mouth screw capped plastic bottles. A drop of toluene was added to each urine sample to inhibit bacterial growth and to minimize bad odour. The samples were brought to the laboratory and kept at 4 osub C till analyzed. Iodine in urine was then determined by the arsenite method following dry ashing in presence of potassium carbonate[11] maintaining Internal Quality Control having a known concentration range of iodine content with each batch of test samples.
Thiocyanate in Urine : Thiocyanate content in the urine was measured following the method of Aldridge[12] and modified by Michajlovskij and Langer[13]. The people of the studied areas were also interviewed regarding the consumption of cyanogenic foods for the identification of thiocyanate load.
Iodine in Salt and Water : To monitor the iodine content of salt samples available in the area, 35 marked air-tight plastic containers were distributed[14] at random to the students of the studied schools and they were asked to bring edible salt samples from their households the next day. The salt samples were kept at room temperature in the laboratory and iodine content was measured within a week by iodometric titration method[15].
The sources of dietary iodine are water, food and the iodised salt available in the studied area. Iodine content in water of a region truly reflects the bioavailability of iodine. Fifteen drinking water samples were collected at random (5 samples from each area) in screw capped plastic bottles. The samples were brought to the laboratory, kept at 4 osub C till analyzed. The iodine level was then determined by the method of Karmarkar et al[11].
For the analysis of data mean, median and standard deviation have been used.
Results
Goitre Prevalence : In all 961 school children from 3 study areas were clinically examined for goiter and the total goitre rate was 34.96%. Area wise goitre prevalences are given in table1. A progressive increase in goitre prevalence was found from the age group of 6 years till the age of 8 years followed by a short decline from the age of 9 to 10 yrs and then again increased upto 12 years. Most of the goitre were of Grade 1 (32.15%) but Grade 2 was also seen in the selected population. Age specific goitre prevalence is shown in table2.
Iodine in Urine : Pattern of urinary iodine excretion of the studied population from the 3 areas of Imphal West is shown in table3. In all, 120 urine samples were collected taking 40 from each area. 25% of total samples had iodine excretion level below 10 μg/dl and 6.7% had iodine level below 5 μg/dl while the median urinary iodine (MUI) was 14.75 μg/dl.
Thiocyanate in Urine : The urinary thiocyanate level is also shown in table3. The mean urinary thiocyanate level was 0.839 ± 0.33 mg/dl indicating that the entire studied population was exposed to thiocyanate load.
Iodine in Salt and Drinking Water : Iodine content in edible salt fortified with iodine was measured and it was found that all the salt samples tested had iodine. 2.9% salt samples had iodine level below 15 ppm, 15.2% salt samples had iodine level above 15 ppm but below 30 ppm and 81.9% salt samples had iodine level more than or equal to 30 ppm table4.
Iodine content in drinking water of the studied region was determined from different water sources in the localities and the mean iodine value was 2.3 ± 0.4 μg/l table4.
Discussion
The most widely accepted marker to evaluate the severity of IDD in a region is the prevalence of endemic goitre in school children. On the basis of its prevalence, WHO/UNICEF/ICCIDD[14] recommended the criteria to understand the severity of IDD as a public health problem in a region. According to these criteria, a prevalence rate of 5.0 - 19.9% is considered as mild; 20.0 - 29.9% as moderate and a prevalence rate of above 30% is considered as a severe public health problem.
Goitre is prevalent at endemic level in all study areas even years after salt iodization program among children and this was evidenced by total goiter rate of 34.96% (Grade 1: 32.15%; Grade 2: 2.81%) in the studied areas indicating that IDD is still a severe public health problem in this region.
The present findings of the urinary iodine excretion level revealed that the studied population had no biochemical iodine deficiency, which has been shown by median urinary iodine of 14.75 μg/dl, and 6.7% population had iodine level below 5 μg/dl. It may be mentioned that a median urinary iodine concentration of 10μg/dl and not more that 20% of the samples are below 5μg/dl in an area indicates no iodine deficiency.[14]
WHO/UNICEF/ICCIDD further recommends that 90% of the household salts should get iodized at the recommended level of 15ppm[16] but the study shows that more than 95% of the households are consuming salts at adequate level.
An indication in the iodine content of the soil can be given by the local drinking water concentration.[1] Iodine content in drinking water indicates that study region is environmentally iodine deficient or the soil is poor in iodine according to Zeltser et al.[17]
The consumption of cyanogenic plant foods was also evident from the urinary excretion of thiocyanate (SCN). In India, large number of cyanogenic plants (SCN precursors) are used as common vegetables and IDD thus persists in many regions inspite of recommended iodine intake.[5], [18],[19] Indian cyanogenic plant foods that are used as common vegetables have potent anti-thyroid activity and supplementation of extra iodine even fails to counteract their effect.[20] In a recent country wide study conducted by Marwaha et al (2003) reported that thiocyanate appers to play an important role in goitre formation especially among poor children in India in post iodisation phase [21]. It has been mentioned that mean value obtained from non-endemic population was 0.504 ± 0.197 mg/dl. The people of Manipur not only consume the common cyanogenic plant foods as vegetables but they also consume almost regularly bamboo shoot as pickle and sometimes as food by poor people containing large amount of thiocyanate precursors namely, cyanogenic glucosides, thioglucosides and thiocyanate. In our present study, the mean urinary thiocyanate value was 0.839 ± 0.33 mg/dl. So, the involvement of thiocyanate or thiocyanate precursors present in food consumed by the people of the region may not be ruled out.
The study, therefore, indicates that the presence of goitrogenic/anti-thyroidal substances may have the possible roles for the persistence of endemic goiter in this region and their action may not be antagonized by iodine supplemented at present level.
References
1. Hetzel BS. An overview of the prevention and control of iodine deficiency disorders. In. Hetzel BS, Dunn JT, Stanbury JB, editors. The Prevention and Control of Iodine Deficiency Disorders ; Elsevier, Amsterdam, 1987: p. 7-31.
2. Levin HM. Economic dimensions of iodine deficiency disorders. In Hetzel BS, Dunn JT and Stanbury JB, editors. The Prevention and Control of Iodine Deficiency Disorders ; Elsevier, Amsterdam, 1987: 195-208.
3. National iodine deficiency disorders control program: National Health Program Series 5. Published by Department of Communication, National Institute of Health and Family Welfare, New Delhi, 2003: p 99.
4. Chandra AK, Ray I. Dietary supplies of iodine and thiocyanate in the etiology of endemic goiter in Tripura. Indian J Pediatrics 2001; 68: 399-404.
5. Kochupillai N. Neonatal hypothyroidism in India. Mount Sinai Journal of Medicine 1992; 59(2): 111-115.
6. Pandav CS, Malik A, Anand K, Pandav S, Karmarkar MG. Prevalence of iodine deficiency disorders among school children of the national capital territory of Delhi. ICCIDD, Regional office of South Asia and Pacific, New Delhi (1996).
7. WHO/SEARO. Iodine deficiency disorders in South East Asia, SEARO, Regional Health. New Delhi, 1985: p. 10.
8. Cochran WG. Sampling techniques, Edition 3, Wiley Eastern Limited, Calcutta (1977).
9. Dunn JT, Crutchfield HE, Gutckunst R, Dunn AD. Iodine deficiency disorders and urinary iodine levels. In. Methods of measuring iodine in urine. The Netherlands: ICCIDD/UNICEF/WHO 1993: 7-10.
10. WHO/UNICEF/ICCIDD. Indicators for assessing Iodine Deficiency Disorders and their control through salt iodization. WHO/NUT/94.6, 1994.
11. Karmarkar MG, Pandav CS, Krishnamachari KAVR. Principle and Procedure for Iodine Estimation . A laboratory manual, Indian Council of Medical Research, New Delhi, 1986.
12. Aldridge WN. The estimation of micro quantities of cyanide and thiocyanate. Analyst , London, 1945; 70: 474-475.
13. Michajlovskij N, Langer P. Studien uber Benziehungen Zwischen Rhodanbildung und Kropfbildender Eigenschaft Von Nahrungsmitteln. I: Gehalt einiger Nahrungs Mittel an praformierten Rhodanid. Z Physiol Chem 1958; 312: 26-30.
14. Indicators for Trackling Progress in IDD Elimination. In IDD Newsletter 1994; 10: 37-41.
15. Titration methods for salt iodine analysis. In Monitoring Universal salt iodization programme (Edition Sullivan KM, Houston E, Gorestein J, Cervinskas J). UNICEF/ ICCIDD/PAMM/WHO, 1995: p 11.
16. ICCIDD/UNICEF/WHO. Assessment of iodine deficiency disorders and monitoring their elimination, A guide for programme managers, Second edition, WHO/NHD/01.1, 2001.
17. Zeltser ME, Aldarkhanov BA, Berezhnaya IM, Spernasky GG, Bazarbekova RB, Nurbekova AA, Levina SA, Mandrovnaya NV, Aripova AA. Iodine deficiency and its clinical manifestation in Kazakhastan. IDD Newsletter 1992; 8 (1): 5-6.
18. Delange F, Thilly C,Bourdoux P, Hennart P, Courtois P, Ermans AM. Influence of dietary goitrogens during pregnancy in humans on thyroid function of the newborn. In. Delange F, Iteke FB, Ermans AM eds. Nutritional Factors Involved in The Goitrogenic Action of Cassava . IDRC-184e, Int Dev Res Cent, Ottawa, 1982; p. 40-50.
19. Chandra AK, Ray I. Evaluation of the effectiveness of salt iodization status in Tripura, northeast India. Indian J Med Res 2002; 115: 22-27.
20. Chandra AK, Mukhopadhyay S, Lahari D, Tripathy S. Goitrogenic content of cyanogenic plant foods of Indian origin and their anti-thyroidal activity in vitro. Indian J Med Res 2004; 119: 180-185.
21. Marwaha RK, Tandon N, Gupta N, Karak AK, Verma K, Kochupillai N. Residual goitre in the postiodization phase: iodine status, thiocyanate exposure and autoimmunity. Clin Endocrinol 2003; 59 (6): 672-681.(Chandra Amar K, Singh L H)