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

Abstract

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 T3 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 T3 available to the developing fetal brain.

MECHANISMS IN ENDOCRINOLOGY: Maternal thyroid dysfunction during pregnancy and behavioural and psychiatric disorders of children: a systematic review

“…Based on the title screening, 850 records were eligible for abstract screening, of which 60 articles met the criteria for full article review. Following thorough review of the articles, 13 (26,27,28,29,30,31,32,33,34,35,36,37,38) remained eligible ( Fig. 1).…”

Treatment of Subclinical Hypothyroidism or Hypothyroxinemia in Pregnancy

“…25,26 In the Generation R Study, 8-year-old children of women from an iodine-deficient geographic area who had been identified with hypothyroxinemia before 20 weeks of gestation were found to have higher ADHD index scores than children of women without hypothyroxinemia. 26 This association persisted after adjustment for IQ.…”

Maternal Thyroid Autoimmunity During Pregnancy and the Risk of Attention Deficit/Hyperactivity Problems in Children: The Generation R Study

“…In addition, there is evidence for the association between thyroid function and attention deficit/hyperactivity disorder (ADHD) (11)(12)(13). Previously, we reported that maternal thyroid dysfunction in early pregnancy predicted impaired cognition and attention deficit/hyperactivity problems in preschool children (14,15).…”