OBJECTIVE: To study the associations between intakes of iodine and water chemicals and the thyroid gland status of schoolchildren living in the coastal city of Port Sudan.
DESIGN: In our previous nationwide study on goitre, it was observed that the prevalence of goitre was high in Port Sudan city despite high urinary iodine excretion. A cross-sectional study including schoolchildren aged 6–12 years was designed. Measurements determined the prevalence of goitre, urinary iodine concentration and thiocyanate secretion in casual urine samples, serum levels of thyroxine, triiodothyronine, thyroid-stimulating hormone and thyroglobulin, as well as the levels of Cl-, F-, Ca²+, Mg²+ and total hardness of drinking water.
SUBJECTS: Schoolchildren (n 654) aged 6–12 years.
SETTING: Port Sudan city is located at the western bank of the Red Sea. The city is surrounded by a mountainous area known as the Red Sea Hills. It is the main sea port in the Sudan, inhabited by ethnically and socio-economically heterogeneous populations.
RESULTS: The prevalence of goitre in Port Sudan was 34.86% while the median urinary iodine concentration was 46.4 ug/dl. Out of thirty-one pupils from Port Sudan, twenty-four (77.42 %) were found to have urinary iodine concentration greater than 30 ug/dl and twelve (38.71 %) had different degrees of biochemical hypothyroidism. Excessive concentrations of Cl-, Ca²+, Mg²+ and water hardness (369.2, 116.48, 60.21 and 539.0 mg/l, respectively) were detected in drinking water samples collected from Port Sudan that exceeded levels permitted by the WHO.
CONCLUSIONS: The coastal city of Port Sudan is a goitre-endemic area. In contrast to other Sudanese cities in which endemic goitre is related to iodine deficiency, goitre in Port Sudan is associated with iodine excess. Water chemicals seemed to have no effects on thyroid status.
Table 2 shows the correlation between various clinical indicators of thyroid function in schoolchildren and the concentration of water chemicals in Port Sudan. It indicates that thyroid hormones (T3 and T4) were poorly correlated with the concentration of water chemicals. TSH was significantly correlated with F– concentration (r=0.506, P=0.004) and inversely correlated with Ca2+ concentration (r=-0.506, P=0.004) and hardness (r=-0.506, P=0.004).