Iodide and fluoride are essential elements. Individual iodide and fluoride intake are dependent on the environment.
Whether fluoride affects the thyroid is still debatable, as well as the possible mechanism underlying any effect remains unknown. At the same time there is a discussion about the effect of iodine on thyroid.
Chinese scientists from the Department of Endocrinology and Metabolism, Institute of Endocrinology, China have studied the effect of both fluoride and iodine on thyroid. Results demonstrate that fluoride can affect both the function and structure of the thyroid but that the effects are in general minor for fluoride than for iodide.
Iodide causes a greater damage to the thyroid than fluoride. But the two elements can function synergistically to induce cytotoxicity. This might be due to the fact that the toxicity occurs though different mechanisms.