Effects of chlorine dioxide on thyroid function in the African green monkey and the rat

Abstract
In a previous study from this laboratory, chlorine dioxide (ClO 2 ) treated drinking water depressed thyroxine (T 4 ) levels in the African green monkey. The present study again demonstrated a decrease in T 4 levels in the same species after 4 wk of oral exposure. However, after 8 wk of treatment T 4 levels rebounded to above pretreatment levels, coinciding with an increase in thyroid radioiodide uptake. This T 4 rebound phenomenon and increased iodide uptake may be due to a compensatory endocrinological mechanism. In rats, T 4 levels dropped during the 8‐wk ClO 2 treatment period in a dose‐dependent manner, and no rebound effect was observed. Iodide uptake values in the rat were not affected. It appears that ClO 2 may have an effect on thyroid function in both species.