Fluoride Action Network



  • TSH is not related IQ in children with different urinary iodine concentrations.
  • Dopamine in plasma is unrelated to IQ in children with adequate or excessive iodine.
  • Dopamine has positive correlation with intelligence in iodine deficiency group.
  • The interaction between dopamine in plasma and TSH is not related to IQ in children.

Environmental iodine deficiency or excess can lead to inappropriate iodine nutrition in the population. Little research has been performed to determine whether changes in thyroid-stimulating hormone (TSH) and/or dopamine (DA) concentrations in peripheral blood are involved in intellectual impairment caused by inappropriate iodine nutrition. 498 children aged 7-12 from areas with different water iodine concentrations were included in the study. Children’s intelligence and levels of urinary iodine and fluoride, TSH, free triiodothyronine (FT3), free thyroxine (FT4), and DA were evaluated. The relationship between TSH and/or DA levels and intelligence quotient (IQ) in all participants and in the population with different urinary iodine concentrations (UIC) was evaluated by multivariate regression analysis. The proportion of people with low average and lower intelligence in UIC 300 >g/L group was significantly higher than that in control group but only a positive correlation was found between DA and IQ in the population with UIC < 100 ug/L (bootstrapped estimation P = 0.032). TSH and/or DA in peripheral blood may be not involved in the progressive decline in intelligence caused by iodine excess but DA had positive correlation with intelligence in iodine deficiency group, and no relationship between TSH concentration and IQ was found in the general population or in different UIC groups.

    *Original abstract online at https://www.sciencedirect.com/science/article/abs/pii/S0304394020302512