Vitamin E management of oxidative damage-linked dysfunctions of hyperthyroid tissues

Thyroid hormones affect growth, development, and metabolism of vertebrates, and are considered the major regulators of their homeostasis. On the other hand, elevated circulating levels of thyroid hormones are associated with modifications in the whole organism (weight loss and increased metabolism and temperature) and in several body regions. Indeed, tachycardia, atrial arrhythmias, heart failure, muscle weakness and wasting, bone mass loss, and hepatobiliary complications are commonly found in hyperthyroid animals and humans.

Most thyroid hormone actions result from influences on transcription of T3-responsive genes, which are mediated through nuclear receptors. However, there is significant evidence that tissue oxidative stress underlies some dysfunctions produced by hyperthyroidism.

During the last decades, increasing interest has been turned to the use of antioxidants as therapeutic agents in various diseases and pathophysiological disorders believed to be mediated by oxidative stress. In particular, because elevated circulating levels of thyroid hormones are associated with tissue oxidative injury, more attention has been paid to explore the application of antioxidants as therapeutic agents in thyroid related disorders.

At present, vitamin E is among the most commonly consumed dietary supplements due to the belief that it, as an antioxidant, may attenuate morbidity and mortality. This is due to the results of numerous scientific studies, which demonstrate that vitamin E has a primary function to destroy peroxyl radicals, thus protecting polyunsaturated fatty acids biological membranes from oxidative damage. However, results are also available indicating that protective vitamin E effects against oxidative damage can be obtained even through different mechanisms.