Thyroglobulin as a proxy for iodine status in pregnancy

Iodine is a component of thyroid hormones and essential for neurological development. To evaluate the iodine nutritional status of pregnant women residing in Veneto and the possible role of thyroglobulin (Tg) as a proxy. 528 pregnant women in the third trimester of pregnancy were consecutively enrolled in this cross-sectional study and were asked to provide an early-morning spot urine sample (for UI/Creat) and a blood sample (for thyroid function and Tg). They also completed a questionnaire. Infant anthropometric data at birth were obtained. Median UI/Creat was 112·8 μg/g. 34·1 % of women had a UI/Creat ≥ 150 μg/g. Iodised salt (IS) was used by 76·9 % of women, iodine-containing supplements (ICS) by 74·2 % and cow's milk was regularly consumed by 46·0 %. At multivariable analysis, consumption of regular cow's milk and ICS were significant predictors of UI/Creat ≥ 150 μg/g (OR 1·57, 95 % CI: 1·06, 2·32 and OR: 2·83, 95 % CI: 1·66, 4·82, respectively). The median Tg value was lower among the iodine-sufficient than among the iodine-deficient women (P = 0·005). At multiple linear regression analysis, Tg was among the factors associated with weight (β = -81·83, P < 0·001) and length (β = -0·3, P < 0·01) at birth, although weakly. Tg was a factor associated with pre-term delivery (OR: 1·52, 95 % CI: 1·20, 1·92). Regular use of cow's milk and ICS is a factor associated with UI/Creat ≥ 150 μg/g. Tg was associated with iodine status and pregnancy outcomes, although it had only a modest discriminative ability for sufficiency.