Although observational evidence suggests that concentrations of selenium , zinc , and iron are positively associated with iodine status , data from r and omized controlled trials fail to confirm this relationship .
Context The metabolism of thyroid hormones , which are essential for normal development , involves many proteins and enzymes .
It requires iodine as a key component but is also influenced by several other micronutrients , including selenium , zinc , iron , and vitamin A. Objective This systematic review was design ed to investigate the effect of micronutrient status and supplementation on  iodine status and thyroid hormone concentrations .
Iodine and iron status of pregnant women in Lubumbashi, Democratic Republic of Congo.
OBJECTIVE Adequate iodine and Fe intakes are imperative during pregnancy to prevent fetal defects , but such data are not available in the Democratic Republic of Congo . We aim ed to assess iodine and Fe status in pregnant women from Lubumbashi . DESIGN Cross-sectional study . We measured urinary iodine concentration ( UIC ) in r and om urine sample s using a modified S and ell – Kolthoff digestion method ; the WHO reference medians were used to classify iodine intake as deficient , adequate , more than adequate or excessive . Serum ferritin concentrations were measured by immunoenzymatic assay and considered insufficient when , 12 ng/ml . SETTING Maternity units from rural , semi-urban and urban areas of Lubumbashi , Democratic Republic of Congo . SUBJECTS Two hundred and twenty-five r and omly selected pregnant women attending prenatal consultation , seventy-five postpartum women and seventy-five non-pregnant women as controls . RESULTS Overall median UIC in pregnant women was 138 ( interquartile range : 105–172 ) mg/l , indicating iodine deficiency , whereas postpartum and nonpregnant women had adequate iodine intake : median UIC5144mg/l and 204mg/l , respectively . Median UIC values were lower in late pregnancy than in early pregnancy : in the first , second and third trimester respectively 255mg/l , 70mg/l and 88mg/l in the rural area ; 306mg/l , 166mg/l and 68mg/l in the semi-urban area ; and 203mg/l , 174mg/l and 99mg/l in the urban area . Fe was insufficient in 39 % of pregnant women compared with 21 % of non-pregnant and postpartum women . In the third trimester , deficiencies in both iodine and Fe were high : 40 % , 12 % and 18 % in the rural , semi-urban and urban areas , respectively . CONCLUSIONS Our data suggest that pregnant women are at risk of iodine and Fe deficiencies in Lubumbashi . Country policies fighting against iodine and Fe deficiencies during pregnancy should be reinforced
Although observational evidence suggests that concentrations of selenium , zinc , and iron are positively associated with iodine status , data from r and omized controlled trials fail to confirm this relationship .
Context The metabolism of thyroid hormones , which are essential for normal development , involves many proteins and enzymes .
It requires iodine as a key component but is also influenced by several other micronutrients , including selenium , zinc , iron , and vitamin A. Objective This systematic review was design ed to investigate the effect of micronutrient status and supplementation on  iodine status and thyroid hormone concentrations .