Exposure To Excessive Iodine Levels, Total Thyroid Volume, and Children

Category: Children's Health , Conditions of the Endocrine System

A study published in the April issue of American Journal of Clinical Nutrition investigated the intake of dietary iodine in children from five different continents. Its aim was to study the effects of iodine consumption on the total volume of the thyroid gland.

Iodine is a necessary component of thyroid hormones. It has been established that iodine in excessive levels for a long period of time can disrupt the normal metabolism of thyroid hormones in the adult. The effects of high iodine consumption had not been measured in children.

High iodine can often cause a decrease in the amount of thyroid hormone produced with a reflex increase in thyroid stimulating hormone (TSH) from the brain that causes growth of the thyroid gland resulting in a goiter.

There were 3319 children in the study aged 6-12 years from five continents. The area with the lowest intake of iodine was Switzerland and the highest was a coastal region in Japan. Most of the variance can be accounted for by dietary standards. Thyroid volume was measured in each child using ultrasound and compared to urinary excretion of iodine metabolites.

They found that 11% of children in the study had an iodine intake 2 times the recommended amount. 59% of children in Japan had an intake greater than 2 times, and 39% had an intake greater than 4 times the recommended amount. The study also showed that intake of 2 times the recommended amount was safe and not associated with an increase in thyroid volume, but intakes greater than 2 times were associated with an increase in thyroid volume and a possible increased risk of goiter. In Japan the thyroid volume was 2 times that of the other test sites.

The authors discussed that in children excess iodine is associated with goiter and thyroid dysfunction. In this study levels of thyroid hormones and thyroid stimulating hormone were not assessed, thus no clear conclusion about the incidence of thyroid hormone dysfunction can be assumed. It is clear, however, that increased levels of iodine consumption greater than 2 times the recommended amount do cause an increase in thyroid volume and increased risk for goiter and dysfunction.

Posted by on January 20, 2006 09:34 AM