Radiation emitted from sources that are transmitted through an intermediated medium and absorbed by animal body. Radiation is very high up environmental toxin. Many sources of radiations are mobile phone, computer, UV lamp and torches radiation affected animal’s body organs such as thyroid gland, liver, kidney, etc. Radiations cause oxidative stress and generate free radicals such as hydroxyl radical, superoxide, nitric oxide, hydrogen peroxide radicals etc. These free radicals are unstable and chemically very active acting as an oxidizing agent that causes the morphological and physiological changes in the cells. In thyroid cells, these radicals can contact the other macromolecules and increase to changes in their structure and functions and hypo or hyperthyroidism conditions. An antioxidant our well wisher of damaging cells. Antioxidants inhibit the generation of free radicals and protect the cells. Antioxidants are essential for many enzymatic reactions and also acts as a free radical scavenger.