Glutathione peroxidase (GPx) is an enzyme family with peroxidase activity to protect the organism from oxidative damage. GPx plays an important role in reducing organic hydroperoxides such as lipid hydroperoxides to their corresponding alcohols, or reducing free hydrogen peroxide to water. It therefore guards against oxidative damage to the cell membranes and other oxidant-sensitive sites in the cell. It has been noticed that altered GPx levels correlate with lesions caused by many comment and complex diseases. GPx level is measured in biological samples as a potential indicator for the potential treatment of cancer, diabetes, neurodegenerative and cardiovascular diseases.