REVIEW ERS ' CONCLUSIONS Despite most of the included studies being of low quality , the results suggest that iodine supplementation , especially iodised oil , is an effective means of decreasing goitre rates and improving iodine status in children .
Indications of positive effects on physical and mental development and mortality were seen , although results were not always significant .
Adverse effects were generally minor and transient .
BACKGROUND Iodine deficiency is the main cause of potentially preventable mental retardation in childhood , as well as causing goitre and hypothyroidism in people of all ages .
It is still prevalent in large parts of the world .
OBJECTIVES To assess the effects of iodine supplementation overall , and of different forms and dosages of iodine supplementation separately , in the prevention of iodine deficiency disorders in children .
Serum thyroglobulin and urinary iodine concentration are the most appropriate indicators of iodine status and thyroid function under conditions of increasing iodine supply in schoolchildren in Benin.
Iodine deficiency control programs have greatly reduced iodine deficiency disorders worldwide . For monitoring changes in iodine status , different indicators may be used . The aim of this study was to evaluate the suitability of indicators of iodine status and thyroid function , thyroglobulin ( Tg ) , thyroid-stimulating hormone ( TSH ) and free thyroxine ( FT4 ) in serum , thyroid volume and urinary iodine concentration , in iodine-deficient schoolchildren under conditions of increasing iodine supply . The study was established as a double-blind , placebo-controlled oral administration of a single dose of iodized oil to schoolchildren ( 7 - 10 y old ) , living in an iodine-deficient area of Benin , with an observation period of 10 mo . However , 3 - 4 mo after supplementation , iodized salt became available in the area . The study population therefore comprised an iodized oil-supplemented group  and a nonsupplemented group  , both of which had variable , uncontrolled intakes of iodized salt during the last 6 mo of the study . Initial mean serum concentrations of TSH and FT4 were within the normal range , whereas serum Tg concentration , urinary iodine concentration and thyroid volume were indicative of moderate-to-severe iodine deficiency . At the end of the study , all indicators had improved significantly , except thyroid volume , which had decreased only in the supplemented group . The supplemented group also still had significantly lower serum Tg and higher urinary iodine concentrations than the nonsupplemented group . Serum Tg and urinary iodine concentrations are the indicators most influenced by a changing iodine supply . Current normal reference ranges of serum concentrations of TSH and FT4 are too wide for detecting iodine deficiency in this age group
REVIEW ERS ' CONCLUSIONS Despite most of the included studies being of low quality , the results suggest that iodine supplementation , especially iodised oil , is an effective means of decreasing goitre rates and improving iodine status in children .
Indications of positive effects on physical and mental development and mortality were seen , although results were not always significant .
Adverse effects were generally minor and transient .
BACKGROUND Iodine deficiency is the main cause of potentially preventable mental retardation in childhood , as well as causing goitre and hypothyroidism in people of all ages .
It is still prevalent in large parts of the world .
OBJECTIVES To assess the effects of iodine supplementation overall , and of different forms and dosages of iodine supplementation separately , in the prevention of iodine deficiency disorders in children .