Brain and iodine deficiency in children and adults
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Iodine plays an important role in the synthesis of thyroid hormones, which regulate the metabolic processes in the brain. Iodine deficiency affecting thyroid hormones during this critical periods of brain development result in hypothyroidism and brain damage. Iodine consumption in the geographic locations known to be deficient areas can be below those needed for the brain normal development and both children and adults in these areas can be at risk of brain disorders and mental retardation (Thyroid 2000;10:871–87).
In Toscani, in 6–10 year old children with mild iodine deficiency (64 micrograms/day), the slowing of reaction in movement tasks was observed (Endocrinol Invest 1995;18:57–62) as well as low visual-motor performances, motor skill and perception. These children had low development quotients and IQ (Iodine and the brain. New York: Plenum Press, 1989: 1–379). The IQ in otherwise normal children deficient in iodine is shifted towards low values (Bull World Health Organ 1986;64:547–51; J Nutr, 1999;129:980–7).
Severe endemic iodine deficiency such as in New Guinea, China, Indonesia, and Thailand causes the clinical picture of cretinism with dominant neurological pathologies (Thyroid 1993;3:59–69; Eur J Endocrinol 1997;137:349–55). It has been shown experimentally that the most detrimental is the combination of iodine and selenium deficiencies. In the rat fetuses in such condition, experiments showed the developmental failure of the central nervous system (Nutritional factors involved in the goitrogenic action of cassava. Ottawa: International Development Research Centre, 1982: 74–83).
“Endemic cretinism is now included in the spectrum of the effects of iodine deficiency in a population termed the ‘iodine deficiency disorders (IDDs)’, which also includes a wide range of lesser degrees of cognitive defect that can be prevented by the correction of iodine deficiency. Iodine deficiency is now recognised by the World Health Organization (WHO) as the most common preventable cause of brain damage with in excess of 2 billion at risk from 130 countries.” — Z-P. Chen & B.S. Hetzel (2010). Cretinism revisited. Best Practice & Research Clinical Endocrinology & Metabolism, 24:1, 39-50