Iodine Deficiency Disorders After a Decade of Universal Salt Iodization in a Severe Iodine Deficiency Region in China (Report‪)‬

Iodine is an essential ingredient for the synthesis of thyroid hormones. Iodine deficiency (ID) causes goiter and different forms of physical and mental retardation. Iodine deficiency disorders (IDD) affect the poor, pregnant woman and preschool children (1,2). Normal levels of thyroid hormones are required for neuronal migration and myelination of the foetal brain, and lack of iodine irreversibly impairs brain development (3). Severe ID during pregnancy increases risk for stillbirths, abortions, and congenital abnormalities (4,6). Cross-sectional studies of moderate to severely iodine-deficient children have generally reported impaired intellectual function and fine motor skills. Two meta-analyses estimated that populations with chronic ID experience a reduction in intelligence quotient (IQ) of 12.5-13.5 points (7,8). Iodized salt has been recognized as the most effective way to control and prevent IDD. Universal salt iodization (USI) has been remarkably successful in many countries. Over 30 countries have achieved the goal of USI (90% of households using iodized salt), and many others are on track (1). USI was implemented in China in all counties in 1995. The initial iodization level was set at 50 mg/kg (50 ppm), later reduced in 2000 to 35 ([+ or -]15) ppm after national monitoring of urinary iodine concentration showed this intake to be excessive; the medians of urinary iodine of school children, at provincial level, were over 300 [micro]g/l in 18 and 14 provinces in 1997 and 1999, respectively (9,10). IDD is a significant public health problem in China (11). Monitoring of iodized salt was carried out at county level one time per year in higher iodized salt coverage counties and two time per year in lower iodized salt coverage counties. A national survey in 1995 found the prevalence of goiter among school children to be [+ or -] 10 per cent in 27 of 30 provinces (12). This study was in conducted 1995 when USI was implemented and a decade later in 2005 with the objectives to assess the effects of USI on the status of IDD in a severe iodine deficiency region in China. Material & Methods