Expression of Iodotyrosine Deiodinase in Thyroid and Other Organs in Iodine-Deficient and Iodine-Excess Rats.

In mammals, iodothyronine deiodinase and iodotyrosine deiodinase (IYD) are known to catalyze the reductive dehalogenation. IYD is a critical enzyme in maintaining iodine homeostasis. Advances in the study of iodothyronine deiodinase have been published steadily; research on IYD has been slow on its function and regulation. We studied the expression of IYD in thyroid, liver, and kidney in conditions such as iodine deficiency and excess to determine its regulation and role in iodine recycling. Sixty 4-week-old female Wistar rats were randomly divided into two groups, with each group containing three subgroups. The rats were fed with different iodine intake for 3 months. After 3 months, all the rats were sacrificed, and the expression of IYD in thyroid, liver, and kidney of the rats were determined. We found that the expression of thyroidal IYD in 0.3-fold-iodine intake group was significantly higher as compared with the low-iodine feed control group (p < 0.01), whereas the expression in 6-fold-iodine intake group was significantly decreased as compared with normal-iodine feed control group (p < 0.01). However, the variation of IYD expression in thyroid was not similar to liver and kidney. In conclusion, iodine deficiency results in an increased expression of IYD in thyroid, whereas excess iodine decreases the expression of thyroidal IYD. In humans, daily iodine intake of <75 or >500 μg can affect the expression of thyroidal IYD. The safety range of iodine intake is narrow. In addition, further investigations are required to study the expression and regulation of IYD in various organs.