A Double-blinded Randomised Study of Iodine Supplementation to Lactating Women in an Iodine-sufficient Area in Sweden and Evaluation of Maternal and Neonatal Iodine Levels and Thyroid Function

The aim of the study is to measure urinary milk iodine concentration (MIC), iodine concentration (UIC), thyroid hormones (TSH, FT4) and thyroperoxidase antibodies (TPOab) in breast-feeding women, and UIC in their nursing infants to determine if the levels are adequate, and to see how they can be influenced by 150 ug daily iodine supplementation in breast-feeding women. The hypothesis is that there is a relative iodine deficiency in this sub-population - lactating women and nursing children-, and that this can be influenced by iodine supplementation. Adequate thyroid hormone and iodine levels are very important for small children, when the plasticity of the brain is greatest.

This is as a prospective, double-blind, placebo-controlled study of 221 mothers and their infants. In parallel, 90 age-matched healthy non-pregnant women are recruited. Mothers are randomized to 150 µg/day iodide supplementation or placebo.

Pregnant women are asked for participation on a visit in pregnancy week 37, at the mother health care (MVC) at Mölnlycke and Skövde. The study will run for approximately 3 months for each individual and begins by sampling A (UIC, TSH, FT4, TPOab) at week 37 of the pregnancy, when mothers also get randomized to 150 µg iodine or placebo. New sampling B (UIC, TSH, FT4, MIC ) is collected when the baby is 3 months old. Thereafter the study is completed. In parallel, 90 healthy non-pregnant, non-lactating women in the same age range are recruited and followed with UIC, TSH, FT4, TPOab for 6 months as a control group. In each case a simple questionnaire is filled and blood is also frozen for future analyses.