Investigation of The Possible Role of Goitrogens in The Development of Iodine Deficiency Disorders in Ghana

Abstract

The important role of iodine deficiency in the development of endemic goitre and cretinism is well established. However, it has been found that adequate iodine intake (75-300 μ/day) does not always eradicate goitre. Therefore, it is understandable that other environmental factors, known as goitrogens present in die staple foods or drinking water contribute to the persistence of the disease. This paper reports on the possible role of goitrogens in the development of goitre in Axim (Western region, Ghana), Sekoti(Upper East region, Ghana) and Accra (Greater Accra region, Ghana; Examinations for thyroid size were carried out on 249 school children aged between ten and fourteen years inclusive in Sekoti, 220 in Axim, and 210 in Accra. With the target of analyzing urine sample from at least 10% of those examined for goitre, urinary iodine and thiocyanate analysis were done on43 pupils in Sekoti, 59 in Axim and 55 in Accra. Total goitre prevalence (visible and invisible) ranged from 56.2% in Sekoti, 20.5% in Accra and 17.3% in Axim. Mean urinary iodine levels in Sekoti was 22.93μg/dL, 46.9μg/dL in Axim and 20.5μg/dL in Accra. The mean urinary thiocyanate was 3.30mg/dL, 1.13mg/dL and 1.84mg/dL respectively in Axim, Accra and Sekoti. Based on goitre prevalence alone, Sekoti could be considered a severe endemic goitre area, while Accra Axim could be classified as mild. However, the mean urinary iodine level in all the areas were highly in excess of the 5μg/dl or less defined to be an indication of iodine deficiency. Moreover, goitrous pupils in all the areas were also excreting iodine levels (18.95 Mg I/dl, 47.8μg/dl and 21/42μg I/respectively in Sekoti, Axim and Accra) far higher than would be expected in people with dietary iodine deficiency. It may be concluded that the goitre endemic of the areas of study may be contributed to by goitrogens either in the food or water. The urinary iodine to thiocyanate ratio (I/SCN ratio) was used as an index to the exposure to dietary goitrogens, in this case, thiocyanate. This ratio was found to be almost statistically the same by analysis of variance in the three areas. The mean I/SC ratio in Sekoti was 21. 4 μg/mg; 42.2μg/ing in Axim and 29.1μg/ug in Accra. Since the thiocyanate exposure is almost the same in the three areas, it could suggest that the high incidence of goitre seen in Sekoti may be contributed to by other goitrogens. Analyses of nutrient intakes based on the 24-hour dietary recall method showed that mean protein intakes were adequate and comparable to the Recommended Dietary Allowances, (RDA) in all the areas. However, the mean energy requirements in all three areas were not met. Axim had the lowest (64% of the RDA) while Accra and Sekoti met 74%and 73.7% respectively. The low energy intakes observed especially in Axim may explain the higher incidence of chronic malnutrition. 25% of the children in Axim were found to be stunted (less than 90%of mean height-for-age). Malnutrition was also found to be severe in Sekoti in terms of wasting where 26,-5% of the children examined had weight-for-height values of less than 80% of standard. 17.2% of Sekoti children were also found to be chronically malnourished. Mean vitamin A intake was also found to be low in Sekoti (81%of the RDA) compared with Accra (1460% of the RDA) and Axim 1988%of RDA). Millet and sorghum contributed about 64% of the total daily caloric intakes according to the 24-hour recall. Thus the possible role of the goitrogenic effect of millet in the etiology of the high incidence of goitre in the Upper East cannot be ruled out. A multiple logistic regression analysis revealed that about 90%of the variability in goitre prevalence could be attributed to a low iodine/high thiocyanate ratio (I/SCN ratio) chronic malnutrition and vitamin A deficiency. Another possible contributing factor to the goitre seen in the areas of study may be attributed to polluted drinking water since most of the water samples collected in the study had a high bacterial and coliform counts as well as E. Coli. The findings of this study confirm what has been observed by Ingeenbleek, 1986 that protein energy malnutrition, hypovitaminosis A, and endemic goitre all of which were once considered distinct clinical entities resulting from specific alimentary deficiencies, might soon prove to be closely interrelated nutritional disorders. It is recommended that plasma thyroid hormones and serum vitamin A levels should be measured to confirm the findings of this study.