Dietary supplies of iodine & thiocyanate in the aetiology of endemic goitre in Imphal East district of Manipur, north east India.

BACKGROUND & OBJECTIVE: The present investigation was undertaken to study the iodine nutritional status of school children of Imphal east district in Manipur where endemic goitre persists during post-salt iodization phase along with the investigation of the factors responsible for the occurrence of goitre endemicity. METHODS: A total of 1,286 children (6-12 yr) were clinically examined for goitre from study areas of Imphal east district. A total of 160 urine samples were collected and analyzed to measure urinary iodine and thiocyanate levels. Iodine content was measured in 140 salt samples and 16 drinking water samples. RESULTS: Overall goitre prevalence was about 30 per cent (grade 1-24.7%; grade 2-5.3%) and median urinary iodine level was 17.25 microg/dl. The mean urinary thiocyanate level was 1.073 +/- 0.39 mg/dl. Iodine/thiocyanate ratio (microg/mg) was in the ranges from 15.65 to 22.34. The mean iodine content in drinking water samples was 2.92 +/- 1.75 microg/l and 97.8 per cent of edible salts had iodine level above 15 ppm at the consumption point. INTERPRETATION & CONCLUSION: Our findings showed that in spite of no biochemical iodine deficiency, iodine deficiency disorders (IDD) is a serious public health problem in Imphal east district of Manipur. The consumption pattern of certain plant foods containing thiocyanate (or its precursors) was relatively high that interfere with thyroid hormone synthesis resulting in the excretion of more iodine. Thus, the existing dietary supplies of thiocyanate in relation to iodine may be a possible aetiological factor for the persistence of endemic goitre in the study region during post salt iodization period.

Role of goitrogens in iodine deficiency disorders & brain development.

Although iodine deficiency has primarily been implicated in the causation of goitre, the significant role played by food goitrogens in the etiology of iodine deficiency disorder (IDD) is being increasingly recognized. Impaired brain development is the major cause of concern in IDD. Detailed experimental studies were undertaken to ascertain various biochemical changes associated with developing brain in response to treatment with a goitrogens--thiocyanate. Addition of thiocyanate to food deprived of KI brought down significantly the circulating levels of thyroxine (T4) in rats. Nucleic acids and protein content in different regions of brain were significantly lowered in rat pups exposed to thiocyanate. The rate of microtubule assembly, which is detrimental for neurite growth was considerably lowered, thereby influencing both myelin deposition and synaptogenesis in developing brain. Goitrogen intake not only caused an adaptive increase in the activity of type II 5'-deiodinase, which governs availability of triiodothyronine (T3) in brain, it also increased the latter's binding to brain nuclear receptors under conditions of thiocyanate induced hypothyroid state. Addition of adequate quantities of KI mitigated thiocyanate induced alterations by restoring circulating level of thyroxine. These investigations suggest that goitrogens play a significant role in influencing biochemical events unique to developing brain.