Associations between thyroid dysfunction and developmental status in children with excessive iodine status

Abstract

Background and objectiveAdequate iodine status and normal thyroid hormone synthesis are important for optimal child development. In this study, we explored whether young children’s developmental status is associated with thyroid dysfunction in an area of chronic excessive iodine exposure.MethodsWe included 298 children between 18 and 48 months of age residing in Algerian refugee camps. Early child development was measured using the Ages and Stages Questionnaires, third edition (ASQ-3), consisting of five domains: Communication, Gross Motor, Fine Motor, Problem Solving and Personal-Social. Due to poor discriminatory ability in the Gross Motor domain, the total ASQ-3 scores were calculated both including and excluding this domain. Urinary iodine concentration (UIC), thyroid hormones (TSH, FT3 and FT4), thyroid antibodies and serum thyroglobulin (Tg) were measured.ResultsThe median UIC was 451.6 μg/L, and approximately 72% of the children had a UIC above 300 μg/L. Furthermore, 14% had thyroid disturbances, of whom 10% had TSH outside the reference range. Children with thyroid disturbances and TSH outside the reference ranges had lower odds of being among the 66% highest total ASQ scores, with adjusted odds ratios (95% CI) of 0.46 (0.23, 0.93) and 0.42 (0.19, 0.94), respectively.ConclusionWe found an association between thyroid dysfunction and poorer developmental status among children with excessive iodine intake. The high iodine intake may have caused the thyroid dysfunction and hence the delayed developmental status; however, other influential factors cannot be excluded. Optimal child development is important for a sustainable future. With iodine excess being an increasing problem globally, this subject should be further explored.

Effect of Excess Iodine Intake from Iodized Salt and/or Groundwater Iodine on Thyroid Function in Nonpregnant and Pregnant Women, Infants, and Children: A Multicenter Study in East Africa

“…Although infants may be particularly vulnerable to excessive iodine intake (7,65,71), no thyroid dysfunction was observed in this study, suggesting that the infant thyroid may adapt to high iodine intake when chronic. However, the longterm consequences of thyroidal stress during infancy are uncertain, and the results conflict with findings elsewhere (10,72,73). Long-term follow-up of infants exposed to excessive iodine intake for long periods is required.…”

Assessment of Public Knowledge regarding the Differences between Hyperthyroidism and Hypothyroidism

“…Thyroid hormones, thyroxin (T 4 ) and triiodothyronine (T 3 ), are essential for the synthesis of growth hormones, cell differentiation, and metabolism, and they are crucial for the growth and development (1) . Both iodine deficiency and iodine excess are known to interfere with thyroid hormone synthesis (2,3) .…”

Trace Element Concentrations in Drinking Water and Urine among Saharawi Women and Young Children

“…High iodine concentration in urine among women and children has previously been examined and published [ 21 , 23 , 39 ]. These studies found a high prevalence of biochemically assessed thyroid dysfunction among both women and children, which might have been caused by excessive iodine intakes.…”