Testicular Protection From Thyroid Hormone Mediated Oxidative Stress

Testis is very rich in unsaturated fatty acids with poor antioxidant defense system and due to presence of a potential reactive oxygen species (ROS)-generating systems, it is much more vulnerable to oxidative damage than other tissues. Thyroid hormones are well known to regu la te s te ro idogenes is and spermatogenesis, thereby, affecting male fertility. In the presence of disturbed thyroid conditions, in hyperthyroidism as well as hypothyroidism testis is much more susceptible to oxidative stress. The increase of testicular oxidative stress marked by elevated MDA or TBARS levels, lipid hydroperoxide, hydrogen peroxide or protein carbonyl contents along with disturbed antioxidant enzyme levels happens during L-thyroxine or tri-iodothyronine induced hyperthyroidism. The reduction of testicular oxidative stress can be achieved either by increasing glutathione contents through administration of melatonin or by vitamin E and/or curcumin or by elevating of levels of antioxidant defence enzymes like SOD, CAT or GPx through administration of vitamin E and/or curcumin. In contrast, during hypothyroidism, the extent of testicular oxidative stress is marked by elevation in rat testicular mitochondrial membrane protein carbonylation, lower GSH contents and dec reased an t iox idan t enzyme leve ls . Hypothyroidism-induced oxidative stress condition could not be reversed with T3 treatment. Furthermore, such oxidative stress condition is not nullified still after withdrawal of reversible goitrogen PTU. Besides, in case of transient hypothyroidism, the oxidative stress condition is prevailed as marked by decreased antioxidant enzymes like SOD, CAT, GPx and GR levels and that might be responsible for triggering germ cell apoptosis in transient hypothyroid rats results in reduction in sperm count.