Attention deficit and hyperactivity disorders in the offspring of mothers exposed to mild-moderate iodine deficiency:: A possible novel iodine deficiency disorder in developed countries

Over a period of almost 10 yr, we carried out a prospective study of the neuropsychological development of the offspring of 16 women from a moderately iodine-deficient area ( area A) and of 11 control women from a marginally iodine-sufficient area ( area B) whose thyroid function had been monitored during early gestation. Attention deficit and hyperactivity disorder (ADHD) was diagnosed in 11 of 16 area A children (68.7%) but in none from area B. Total intelligence quotient score was lower in area A than in area B children (92.1 +/- 7.8 vs. 110 +/- 10) and in ADHD children when compared with both non-ADHD children from the same area and control children (88.0 +/- 6.9 vs. 99.0 +/- 2.0 and 110 +/- 10, respectively). Seven of 11 ADHD children (63.6%) were born to the seven of eight area A mothers who became hypothyroxinemic at early gestation, whereas only one of five non-ADHD children was born to a woman who was hypothyroxinemic at 20 wk of gestation. So far, a similar prevalence of ADHD has been reported only in children with generalized resistance to thyroid hormones. This might suggest a common ADHD pathogenetic mechanism consisting either of reduced sensitivity of the nuclear receptors to thyroid hormone ( generalized resistance to thyroid hormones) or reduced availability of intracellular T(3) for nuclear receptor binding. The latter would be the ultimate consequence of maternal hypothyroxinemia ( due to iodine deficiency), resulting in a critical reduction of the source of the intracellular T(3) available to the developing fetal brain.