Is Neuropsychological Development Related to Maternal Hypothyroidism or to Maternal Hypothyroxinemia?

Abstract

Several recent publications have drawn attention to the role of the thyroid hormone status of the mother on the future neuropsychological development of the child.The screening of pregnant women for clinical or subclinical hypothyroidism based on second trimester elevated maternal TSH values has been proposed.Here, we have summarized present epidemiological and experimental evidence strongly suggesting that conditions resulting in first trimester hypothyroxinemia (a low for gestational age circulating maternal free T 4 , whether or not TSH is increased) pose an increased risk for poor neuropsychological development of the fetus.This would be a consequence of decreased availability of maternal T 4 to the developing brain, its only source of thyroid hormone during the first trimester; T 4 is the required substrate for the ontogenically regulated generation of T 3 in the amounts needed for optimal development in different brain structures, both temporally and spatially.Normal maternal T 3