Thyroglobulin as a proxy for iodine status in pregnancy

Iodine is a component of thyroid hormones and essential for neurological development. Objective: 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. Iodized 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, regular cow's milk consumption and ICS use were significant predictors of UI/Creat ≥150 μg/g (odds ratio (OR) 1.57, 95% confidence interval (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 were factors 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.