Studies on the etiology of endemic goiter in the Sudan : The role of pearl millet

Abstract: Endemic thyroid disorders (ETD) are major health problems worldwide. Although the major role of iodine deficiency in the etiology of ETD is well founded, other factors have been shown to contribute to its etiology as well.The objectives were to investigate factors other than iodine deficiency which contribute to the etiology of endemic goiter in Sudan with special reference to the suggested potential goitrogenicity of pearl millet using both a classical goiter survey and animal feeding studies.The prevalence of goiter in preschool children from a population subsisting on sorghum and pearl millet was found to be 22.3% despite normal median urinary iodine excretion (10 µg/dl). Mean serum thyroxine (T4) and triiodothyronine (T3) levels were found to be in the normal ranges and median serum thyrotropin (TSH) and mean urinary thiocyanate levels were found to be high.When two different pearl millet cultivars were fed to rats, only one of them induced a significant increase in the weight of the thyroid gland compared to feeding a casein control or wheat reference diets and feeding the fermented form of this cultivar induced a further increase and an increase in serum T3 as well. Feeding of the fermented form of the other cultivar induced a significant increase in both serum T4 and T3. Concomitantly the fermentation procedure reduced the ash contents of pearl millet and removed considerable amounts of Mg. Mean serum selenium levels were found to be high in rats fed theunfermented millet and even higher in those fed the fermented millet diets than in rats fed control or reference diets. Among nine different millet cultivars (3 brown, 3 yellow and 3 gray) only feeding of the gray seeded millet cultivars induced significant increases in the weight of the thyroid gland in rats. When the thyroid glands of rats fed four millet cultivars (unfermented and fermented) were evaluated microscopically, small thyroid follicles with decreased follicular lumen and cubic or cylindrical thyrocytes were observed in all of these rats. Infiltration of the thyroid gland with lymphocytes was observed mostly in rats fed fermented millet diets. Heat treatment was found to have marked qualitative and quantitative effects on the flavonoid profile in pearl millet.The main conclusions from these studies are that endemic goiter might exist even in the absence of iodine deficiency, that in rats not all pearl millet cultivars are goitrogenic, that traditional fermentation and heat treatment might augment the goitrogenicity of pearl millet and that feeding of pearl millet might induce thyroiditis in rats.