Maternal prenatal iodine deficiency hypothyroidism or hypothyroxinemia impairs intelligence and function of offspring, even when the deficiency is mild.[1],[2],[3] For neonates TSH, rather than T4 is the preferred correlate for measures of neurological/cognitive outcome. [4] Normal infants with TSH levels in the upper quartile of the normal range (4.19-17.0 mU/I)TSH score lower on tests of cognitive and executive function than those in the second quartile (2.05-2.95 mU/I). High-normal TSH has also been negatively correlated with poorer performance on measures of cognitive function and ADHD.[5] Children with urinary I levels <100 µg/L have lower IQ and higher prevalence of behavioral disorders than higher I excreting peers,while mild I deficiency in women is correlated with attention deficit hyperactivity disorders in their children.[6] An increase in congenital hypothyroidism in neonates has been noted in the US. [7],[8] Associations between transient maternal hypothyroxinemia (defined as fT4 lower than the 10th percentile) and exposure to TH-disrupting agents and autism have also been made.[9] The question of whether, and to what degree, iodine-uptake inhibitors increase rates of impairment is unanswered.
[1] Berbel P, Mestre JL, Santmira A, Palazon I, Franco A, Graells M, Gonzalez-Torga A, de Escobar GM. 2009. Delayed neurobehavioral development in children born to pregnant women with mild hypothyroxinemia during the first month of gestation: the importance of early iodine supplementation. Thyroid. 19(5): 511-519. DOI: 10.1089/thy.2008.0341
[2] Pop VJ, Kuijpens JL, van Baar AL, Verkerk G, van Son MM, de Vijlder JJ, Vulsma T, Wiersinga WM, Drexhage HA, Vader HL. 1999. Low maternal free thyroxine concentrations during early pregnancy are associated with impaired psychomotor development in infancy. Clinical Endocrinology. 50(2): 149-155.
[3] Vermiglio F, Lo Presti VP, Moleti M, Sidoti M, Tortorella G, Scaffidi G, Castagna MG, Mattina F, Violi MA, Crisa A, Aremisia A, Trimachi F. 2004. 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. Journal of Clinical Endocrinology and Metabolism. 89(12): 6054-6060.
[4] Oken E, Braverman LE, Platek D, Mitchell ML, Lee SL, Pearce EN. 2009. Neonatal thyroxine, maternal thyroid function and child cognifition. The Journal of Clinical Endocrinology and Metabolism. 94(2): 497-503. doi:10.1210/jc.2008-0936
[5] Pederol-Ivarez M, Ribas-Fito N, Torrent M, Julvez J, Ferrer C, Sunyer J. 2007. TSH concentration within normal range is associated withy cognitive function and ADHD symptoms in healthy preschoolers. Clinical Endocrinology. 66: 890-898. (doi:10.1111/j.1365-2265.2007.02871.x)
[7] Harris KB, Pass KA. 2007. Increase in congenital hypothyroidism in New York State and in the United States. Molecular Genetics and Metabolism. 91: 268-277.
[8] Hinton CF, Harris KB, Borgfeld L, Drummond-Borg M, Eaton R, Lorey F, Therrell BL, Wallace J, Pass KA. 2010. Trends in incidence rates of congenital hypothyroidism related to select demographic factors: data from the United States, California, Massachusettes, New York and Texas. Pediatrics. 125: S37-S47.
[9] Roman G. 2007. Autism: Transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents. Journal of Neurological Sciences. 262(1-2): 15-26.
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