Evaluation of possible goitrogenic and anti-thyroidal effect of nitrate, a potential environmental pollutant.

Nitrate is a wide spread contaminant of ground and surface water. The source of nitrate in the ground water may be from run off or seepage from fertilized soil, municipal or industrial waste water, land fills, septic system, urban drainage or decaying plants. Human and animal systems are affected severely on nitrate exposure. The study was to investigate the effect of dietary nitrate exposure on the thyroid status along with the state of iodine nutrition. Rats were fed diet containing 3% potassium nitrate (KNO3) for 4 weeks and then thyroid status was evaluated by thyroid gland weight, urinary iodine excretion pattern, thyroid peroxidase (TPO) activity, serum levels of total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations. In nitrate treated animals, the weight of thyroid gland was increased significantly (P<0.001) while thyroid peroxidase activity (P<0.01), serum T4 (P<0.01) and serum T3 levels (P<0.001) were reduced; but serum TSH level was increased (P<0.001) along with slightly elevated iodine excretion level (P<0.001) in comparison to control animals. The overall results indicated the development of a relative state of functional hypothyroidism with enlarged thyroid after nitrate exposure. This study can explain a part for the persistence of residual goitre in the post-salt iodization phase.

Iodine nutritional status of the school-age children in South Tripura, North East India.

To evaluate the iodine nutritional status, the thyroids of 3,577 school-age children of both sexes are examined clinically by palpation for goiter prevalence, 345 urine samples are analysed by dry ashing to determine the urinary iodine excretion pattern and 121 edible salt samples collected from house hold are analysed by iodometric titration to monitor the iodinatien achieved through salt from 6 representative areas of South Tripura in goiter endemic North East India. Endemic goiter is found prevalent in all the study areas though its occurrence varies from 13.95% to 30.96%, indicating that clinically mild to severe degree of iodine deficiency prevails in the region. But the pattern of median urinary iodine level of the studied population shows that there is no biochemical iodine deficiency. In 66.94% salt samples had iodine content less than the recommended level of 15 ppm. As per the classification recommended by WHO/UNICEF/ICCIDD, South Tripura falls into goiter endemic by clinical criteria and no endemicity by biochemical criteria. However, iodine deficiency disorders (IDD) continue to be prevalent in the region.