Iodine Status and Thyroid Function in Lactating Women and Infants – a Survey in the Zagreb Area, Croatia

Lactating women (LW) and infants have high dietary iodine requirements and are at risk of iodine deficiency. The aim of the study was to assess iodine status and thyroid function in LW and their breastfed infants in Zagreb, Croatia. The study included 133 LW and breastfed infant pairs. Urinary iodine concentration (UIC) and thyroid function parameters were measured in all subjects. In LW, breast milk iodine concentration (BMIC) was measured and iodine and salt rich food frequency questionnaire data were collected. Results of analysis indicated that 99.2% of the LW used iodized salt in household and 20.4% used iodine-containing vitamin and mineral supplements. Median (IQR) UIC was 75 μg/L (19.0-180.5 μg/L) in LW and 234 μg/L (151.0-367.5 μg/L) in infants, whereas BMIC was 121 μg/kg (87.8-170.8 μg/kg). Multivariate regression analysis revealed BMIC to be a significant predictor of infant UIC (p