The placental barrier fails to fully protect against harmful contaminants, prompting calls for iodine testing in pregnancy and stricter regulatory standards.
At the 2024 Journées Francophones de la Nutrition, held in Strasbourg from December 4 to 6, experts gathered to explore the important topic of contaminants and their effects on the thyroid. Among the key topics was the essential role of maternal thyroid hormones in fetal brain development. Maternal Thyroid Hormones Maternal thyroid hormones are indispensable for proper brain maturation in the fetus, emphasized Jean-Baptiste Fini, PhD, a biologist at the French National Centre for Scientific Research. While severe iodine deficiency during pregnancy, which can cause cretinism, is no longer seen in France, even mild deficiencies can have profound effects on fetal development. A cohort study highlighted the impact of insufficient maternal thyroid hormone levels. Children born to mothers with hypothyroxinemia, either before pregnancy or during the first trimester, were found to have lower IQ scores, reduced gray matter density, and smaller cortical volumes. Placental Barrier and Contaminants Fetal thyroid metabolism can be disrupted by contaminants transmitted through the mother's diet, as the placental barrier does not entirely block certain harmful substances. Numerous studies have investigated the effects of in utero exposure to these contaminants on developmental disorders in children. One epidemiological study identified a correlation between language delays in 30-month-old children and maternal exposure to specific chemicals, as measured in maternal blood and urine samples. Supporting this, experiments with tadpoles exposed to the same chemicals revealed impaired function in multiple genes…