S-09-01 Thyroid hormones, pregnancy and offspring development in humans and correlation to animals

Thyroid hormones have fundamental physiological roles in vertebrate physiology ranging from induction of metamorphosis in amphibians to photoperiodic regulation of seasonal breeding in birds. Thyroid hormones are also essential for maintaining a pregnancy and fetal growth and development. In particular, they are essential for neurological development. It is well established that overt thyroid dysfunction, results in increased fetal loss and impaired offspring development. There is now growing evidence that even borderline variation in maternal thyroid status and variation within the population reference-range during pregnancy is associated with adverse neurological outcomes in offspring. This has important implications at the population level. Iodine is essential for the synthesis of thyroid hormone. Iodine is however, unevenly distributed across the globe and changes in agricultural practices as well as people’s diet has placed a substantial number of individuals at risk from iodine deficiency. This is a particular problem in Europe where not all nations utilise universal salt iodisation. Endocrine disruptors e.g. nitrates, perchlorate and thiocyanate inhibit iodine uptake into the thyroid and can exacerbate iodine deficiency. Taken together the combination of iodine deficiency and endocrine disruption may have substantial deleterious effects on intellectual performance at the population level