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Purpose: Urinary iodine-to-creatinine ratio (UI/Creat) reflects recent iodine intake but has limitations for assessing habitual intake. Thyroglobulin (Tg) concentration, which increases with thyroid size, appears to be an indicator of longer-term iodine status in children and adults, however, less is known in pregnancy. This study investigated the determinants of serum-Tg in pregnancy and its use as an iodine-status biomarker in settings of iodine-sufficiency and mild-to-moderate deficiency. Methods: Stored blood samples and existing data from pregnant women from the Netherlands-based Generation R (iodine-sufficient) and the Spain-based INMA (mildly-to-moderately iodine-deficient) cohorts were used. Serum-Tg and iodine status (as spot-urine UI/Creat) were measured at median 13 gestational weeks. Using regression models, maternal socio-demographics, diet and iodine-supplement use were investigated as determinants of serum-Tg, as well as the association between UI/Creat and serum-Tg. Results: Median serum-Tg was 11.1 ng/ml in Generation R (n = 3548) and 11.5 ng/ml in INMA (n = 1168). When using 150 µg/g threshold for iodine deficiency, serum-Tg was higher in women with UI/Creat < 150 vs ≥ 150 µg/g (Generation R, 12.0 vs 10.4 ng/ml, P = 0.010; INMA, 12.8 vs 10.4 ng/ml, P < 0.001); after confounder adjustment, serum-Tg was still higher when UI/Creat < 150 µg/g (regression coefficients: Generation R, B = 0.111, P = 0.050; INMA, B = 0.157, P = 0.010). Iodine-supplement use and milk intake were negatively associated with serum-Tg, whereas smoking was positively associated. Conclusion: The association between iodine status and serum-Tg was stronger in the iodine-deficient cohort, than in the iodine-sufficient cohort. Serum-Tg might be a complementary (to UI/Creat) biomarker of iodine status in pregnancy but further evidence is needed. [ABSTRACT FROM AUTHOR]

Purpose: The trace element iodine is a vital constituent of thyroid hormones. Iodine requirements increase during pregnancy, when even mild deficiency may affect the neurocognitive development of the offspring. Urinary iodine concentration (UIC) is the means of assessing iodine status in population surveys; a median UIC of 100–199 µg/L is deemed sufficient in a non-pregnant population. Milk is the main dietary source of iodine in the UK and Ireland. Methods: We surveyed the iodine status of 903 girls aged 14–15 years in seven sites across the island of Ireland. Urine iodine concentration was measured in spot-urine samples collected between March 2014 and October 2015. Food group intake was estimated from iodine-specific food-frequency questionnaire. Milk-iodine concentration was measured at each site in summer and winter. Results: The median UIC overall was 111 µg/L. Galway was the only site in the deficient range (median UIC 98 µg/L). All five of the Republic of Ireland sites had UIC ≤ 105 µg/L. In the two sites surveyed twice, UIC was lower in summer vs winter months [117 µg/L (IQR 76–165) vs 130 µg/L (IQR 91–194) (p < 0.01)]. Milk samples collected from Galway and Roscommon had a lower mean iodine concentration than those from Derry/Londonderry (p < 0.05). Milk intake was positively associated with UIC (p < 0.001). Conclusions: This is the largest survey of its kind on the island of Ireland, which currently has no iodine-fortification programme. Overall, the results suggest that this young female population sits at the low end of sufficiency, which has implications if, in future, they enter pregnancy with borderline status. [ABSTRACT FROM AUTHOR]

Background Mild-to-moderate iodine deficiency, particularly in pregnancy, is prevalent; this is of concern because observational studies have shown negative associations with child neurodevelopment. Although neither the benefits nor the safety of iodine supplementation in pregnancy in areas of mild-to-moderate deficiency are well researched, such supplementation is increasingly being recommended by health authorities in a number of countries. Objectives By reviewing the most recent published data on the effects of iodine supplementation in mildly-to-moderately deficient pregnant women on maternal and infant thyroid function and child cognition, we aimed to determine whether the evidence was sufficient to support recommendations in these areas. Methods A systematic review of randomized controlled trials (RCTs), non-RCT interventions, and observational studies was conducted. To identify relevant articles, we searched the PubMed and Embase databases. We defined mild-to-moderate iodine deficiency as a baseline median urinary iodine concentration (UIC) of 50–149 µg/L. Eligible studies were included in meta-analyses. Results In total, 37 publications were included—10 RCTs, 4 non-RCT interventions, and 23 observational studies. Most studies showed no effect of iodine supplementation on maternal or infant thyroid-stimulating hormone and free thyroxine. Most RCTs found that supplementation reduced maternal thyroglobulin and in 3 RCTs, it prevented or diminished the increase in maternal thyroid volume during pregnancy. Three RCTs addressed child neurodevelopment; only 1 was adequately powered. Meta-analyses of 2 RCTs showed no effect on child cognitive [mean difference (MD): −0.18; 95% CI: −1.22, 0.87], language (MD: 1.28; 95% CI: −0.28, 2.83), or motor scores (MD: 0.28; 95% CI: −1.10, 1.66). Conclusions There is insufficient good-quality evidence to support current recommendations for iodine supplementation in pregnancy in areas of mild-to-moderate deficiency. Well-designed RCTs, with child cognitive outcomes, are needed in pregnant women who are moderately deficient (median UIC < 100 µg/L). Maternal intrathyroidal iodine stores should be considered in future trials by including appropriate measures of preconceptional iodine intake. This review was registered at www.crd.york.ac.uk/prospero as CRD42018100277. [ABSTRACT FROM AUTHOR]

Iodine deficiency is present in certain groups of the UK population, notably in pregnant women; this is of concern as iodine is required for fetal brain development. UK milk is rich in iodine and is the principal dietary iodine source. UK sales of milk-alternative drinks are increasing but data are lacking on their iodine content. As consumers may replace iodine-rich milk with milk-alternative drinks, we aimed to measure the iodine concentration of those available in the UK. Using inductively coupled plasma-MS, we determined the iodine concentration of seven types of milk-alternative drink (soya, almond, coconut, oat, rice, hazelnut and hemp) by analysing forty-seven products purchased in November/December 2015. For comparison, winter samples of conventional (n 5) and organic (n 5) cows' milk were included. The median iodine concentration of all of the unfortified milk-alternative drinks (n 44) was low, at 7-3 µg/kg, just 1-7% of our value for winter conventional cows' milk (median 438 µg/kg). One brand (not the market leader), fortified its soya, oat and rice drinks with iodine and those drinks had a higher iodine concentration than unfortified drinks, at 280, 287 and 266 µg/kg, respectively. The iodine concentration of organic milk (median 324 µg/kg) was lower than that of conventional milk. Although many milk-alternative drinks are fortified with Ca, at the time of this study, just three of forty-seven drinks were fortified with iodine. Individuals who consume milk-alternative drinks that are not fortified with iodine in place of cows' milk may be at risk of iodine deficiency unless they consume alternative dietary iodine sources. [ABSTRACT FROM AUTHOR]