AK Chandra, A Bhattacharjee, T Malik and S Ghosh

Iodine deficiency disorders (IDD) refer to a complex clinical and sub clinical disorder caused for the lack of adequate dietary iodine. Iodine deficiency also affects the socioeconomic development of a community(1). In India, IDD constitute a major public health problem. Not a single state or union territory in the country is free from the problem of IDD; out of 587 districts in the country, 282 have been surveyed for IDD and 241 are found to be goiter endemic(2).

In Uttar Pradesh (UP), out of 83 districts, 34 districts have been surveyed for iodine nutriture and 29 districts have been found goiter endemic(3). IDD is not only restricted in the hilly Himalayan mountain areas in India, it has also been reported from the Sub-Himalayan flat lands (Tarai), plains, riverine areas, deltas and even costal regions(4-6). Siddharthnagar district is located in Eastern UP at a distance of about 32-48 kms from the outer range of the Himalayas. Reports on endemic goiter and current state of iodine nutrition are not available from the district and thus the present investigation has been undertaken to evaluate the prevalence of goiter, state of iodine nutrition of the population, distribution of iodine through edible salt as a part of iodization program, bioavailability of iodine and consumption pattern of common goitrogenic food that generally interfere with iodine nutrition.

Selection of study area: The goiter survey was conducted in Siddharthnagar district, located on Indo-Nepal border (area: 2895 sq.km; population: 20 lakhs) between January-July 2006. It has 14 Community Development Blocks (CD Blocks) of which 10 are rural and 4 are urban. The present study was conducted in Naugarh Subdivision which consists of 5 CD Block (1 urban, 4 rural). To get proper representation, 5 areas / localities were selected from 5 CD Blocks taking one from each by purposive sampling method(7). In each study area, at least two primary schools and one junior high school were selected by simple random sampling to get adequate representative target population for goiter survey.

Selection of target population: As per recommendation of WHO/UNICEF/ICCIDD(8), the school children in the age group 6-12 yrs from both sexes were selected, because of their high vulnerability to goiter, easy accessibility and because they are representative of their age group in the community(8). As there is no adequate information on prevalence of goiter in the study area, the sample size has been calculated assuming goiter prevalence of 20% and allowable/permissible error of 10%. A sample size of 1600 was obtained. A total of 1663 school children in the age group 6-12 yrs were included from 19 schools of 5 study areas.

Goiter survey method: All the students of the recommended age group who were present on the days of survey were clinically examined for the enlargement of thyroid (goiter) by trained research staff using palpation method as per recommendations(9). Goiter grading was done as per recommended criteria of WHO/UNICEF/ICCIDD [Grade 0: no goiter; Grade1: thyroid palpable but not visible; Grade 2: thyroid visible with neck in normal position](8). The age of the examined students was recorded from the school register and was rounded off to the nearest whole number.

In each study area, 40 urine samples were collected because measurement of iodine content in 40 samples at random gives a clear idea regarding the consumption pattern of iodine intake of that locality(9). Samples were collected from children of both sexes irrespective of their thyroid status, maintaining proportionate representation from the entire study population. Urine samples were collected in a wide mouth screw capped plastic bottle adding a drop of toluene to inhibit bacterial growth and minimize bad odor. The samples were brought to the laboratory and kept at 4ºC till analyzed. Iodine in the urine was determined by standard methods(10) maintaining internal quality control having a known concentration range of iodine content with each batch of samples.

Measurement of iodine content of at least 35 salt samples collected at random from a locality represent valid estimate about the distribution of iodine through edible salts of the locality(11). Therefore, 35 marked airtight plastic containers were distributed at random to the students of the studied schools and they were asked to bring about 20 g of salt 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(12).

Iodine content in the foods/vegetables grown and consumed by the people of a particular geographic region is dependent on iodine content of the soil that can be assessed by measuring iodine content in drinking water(13). In each study area, 4 water samples at random were collected in clean screw capped plastic iodine free bottles from shallow tube wells (100-150 ft depth), the people use for drinking. The samples were brought to the laboratory and kept at 4ºC till analyzed. The iodine content of drinking water was determined by the method of Karmarkar, et al.(10).

Thiocyanate SCN) content in urine was measured by the method of Aldridge(14) and modified by Michajlovskij and Langer(15), to study the consumption pattern of common goitrogenic foods by the population.

Statistical methods: Mean, standard deviation and median values have been used to describe the data as appropriate. Two-tail chi square test was applied to determine association between prevalence of goiter with age and sex of the school children.

Total goiter rate (TGR) was 30.2%, and most of the goiter was palpable or Grade1 (27.1%) (Table I). Age specific prevalence is depicted in Table II. Goiter prevalence among male and female school children is shown in Table III. Urinary iodine and SCN excretion pattern of the studied population is shown in Table IV. Table V depicts the iodine content of salt samples and drinking water.

No. of salt samples from each area : 35 ; Total salt samples : 175; 
No. of drinking water samples from each area: 4; Total water samples : 20.

Consumption pattern of common goitrogenic food: Iodine concentration in drinking water was 9.5 µg/L of water. In all 200 urine samples were analyzed and the mean urinary SCN level was 0.810± 0.490 mg/dL in the ranges of 0.578 to 1.187 mg/dL (Table IV) indicating that the entire studied population is further exposed to thiocyanate load and their consumption of common goitrogenic food is relatively high.

It was found that mean of I/SCN ratios obtained from all study areas were well above the critical level of 7. However, a total of 22% studied individuals had the I/SCN ratios below or equal to the critical level (Table IV).

In the studied region, the total goiter prevalence was 30.2% (Grade1 - 27.1%; Grade 2 - 3.1%) indicating that IDD is a severe public health problem. There is a significant association between the age of school children and prevalence of goiter. In addition the prevalence among girls was more than boys. The observed result is almost consistent with earlier observations(16,17).

Urinary iodine level is used as a valuable indicator for the assessment of IDD in a region because 90% of body’s iodine is excreted through urine(9). A median urinary iodine concentration of 100 µg/L i.e., 50% of the samples should be above 100 µg/L. When not more than 20% of the samples are below 50 µg/L in an area, it indicates that there is no iodine deficiency in the population(11). In the present study the median urinary iodine concentration was 96 µg/L i.e. below 100 µg/L. Therefore, the studied region is biochemically iodine deficient at present or the people are not getting adequate dietary iodine.

It has been recommended by WHO/UNICEF/ICCIDD that 90% of the household should get iodized salt at the level of 15 ppm(18). The present study showed that 83.4% of the households are consuming salt with inadequate iodine (<15 ppm), 4% households consuming salt without iodine and only 12.6% are consuming salt with recommended level of iodine. In the crystalline salt samples, 99.0% of the samples had iodine level below 15 ppm and in the powdered salt samples, 72.6% had iodine below that recommended value. All these results suggest that there is need to strengthen the system of monitoring the quality of salt to ensure the availability of 15 ppm of iodine at the consumption point or household level.

Iodine content in the drinking water indicates whether the region is environmentally iodine deficient or the soil is poor in iodine. Iodine deficient zones are categorized as severe deficient zone having iodine less than 4 µg/L of water; moderate deficient zone with iodine level 4-10 µg/L of water and the relative deficient zone having iodine level 20 µg/L of water(19). According to these criteria, the studied region should be considered as moderate deficient zone as evidenced by iodine content in drinking water.

Excretion of SCN indicates the consumption pattern of cyanogenic plant foods (such as cabbage, cauliflower, radish, mustard, maze, turnip, sweet potato etc.) of the population in an area. In post iodization phase, thiocyanate appears to have an important role in goiter formation especially among poor children in India(20). It has been mentioned that mean value obtained from non-endemic population was 0.504±0.197 mg/dL. In the present study the mean urinary thiocyanate value was 0.810±0.49 mg/dL that indicates the consumption of cyanogenic plant foods of the population in the studied region is relatively high.

Available literature suggests that development of goiter does not necessarily depends upon the consumption of large quantities of food containing SCN precursors but critically related to the balance between the dietary supplies of iodine and thiocyanate(21). The ratio is higher than 7 under normal condition and endemic goiter develops when it reaches a critical threshold of 3(22). A total of 22% of the studied population had I/SCN ratio below or equal to 7 indicating their susceptibility for the development of goiter. Therefore involvement of thiocyanate or thiocyanate precursors such as goitrin and isothiocyanates present in the food consumed by the people of the studied region may have additional role along with iodine deficiency for the persistence of endemic goiter during post salt iodization phase.

The present study indicates that biochemical iodine deficiency due to intake of less iodine is the main cause for the persistence of IDD in Naugarh sub-division; besides iodine deficiency, the anti thyroidal / goitrogenic substances present in foods may have the additional role for IDD during post salt iodization phase.

Acknowledgement is due to the Principal, Universal College of Medical Sciences, Bhairahawa, Nepal for giving necessary permission to the second author to conduct the research work.