Karbownik Malgorzata, Lewinski Andrzej
Department of Endocrinology and Isotope Therapy, Medical University of Lodz, Lodz, Poland.
Neuro Endocrinol Lett. 2003 Oct;24(5):293-303.
Reactive oxygen species (ROS) play an important role in physiological processes, but - when being in excess - ROS cause oxidative damage to molecules. Under physiological conditions, the production and detoxification of ROS are more-or-less balanced. Also in the thyroid, ROS and free radicals participate in physiological and pathological processes in the gland. For example, hydrogen peroxide (H2O2) is crucial for thyroid hormone biosynthesis, acting at different steps of the process. Additionally, H2O2 is believed to participate in the Wolff-Chaikoff's effect, undergoing in conditions of iodide excess in the thyroid. Much evidence has been accumulated indicating that oxidative stress is involved in pathomechanism of thyroid disease, e.g., Graves' disease, goiter formation or thyroid cancer. Melatonin (N-acetyl-5-methoxytryptamine) - the main secretory product of the pineal gland - is a well-known antioxidant and free radical scavenger, widely distributed in the organism. Mutual relationships between the pineal gland and the thyroid have - for a long time - been a subject of intensive research. The abundant to-date's evidence relates mostly to the inhibitory action of melatonin on the thyroid growth and function and - to a lesser extent - to the stimulatory effects of thyroid hormones on the pineal gland. It is highly probable that under physiological conditions melatonin and, possibly, other antioxidants regulate ROS generation for thyroid hormone synthesis. We believe that melatonin may protect against extensive oxidative damage in the course of certain thyroid disorders or in case of a harmful action of some external factors on the thyroid. Thus, oxidative damage and the protective action of antioxidants, melatonin included, may occur during both physiological and pathological processes in the thyroid, however, this assumption, requires further studies.
活性氧（ROS）在生理过程中发挥着重要作用，但过量时会对分子造成氧化损伤。在生理条件下，ROS的产生和解毒大致平衡。在甲状腺中，ROS和自由基也参与腺体的生理和病理过程。例如，过氧化氢（H2O2）对甲状腺激素的生物合成至关重要，在该过程的不同步骤中发挥作用。此外，H2O2被认为参与了甲状腺碘过量时发生的Wolff-Chaikoff效应。已有大量证据表明，氧化应激参与甲状腺疾病的发病机制，如格雷夫斯病、甲状腺肿形成或甲状腺癌。褪黑素（N-乙酰-5-甲氧基色胺）——松果体的主要分泌产物——是一种著名的抗氧化剂和自由基清除剂，广泛分布于生物体中。松果体与甲状腺之间的相互关系长期以来一直是深入研究的课题。迄今为止的大量证据主要涉及褪黑素对甲状腺生长和功能的抑制作用，以及在较小程度上甲状腺激素对松果体的刺激作用。在生理条件下，褪黑素以及可能的其他抗氧化剂很可能调节甲状腺激素合成过程中的ROS生成。我们认为，褪黑素可能在某些甲状腺疾病过程中或在某些外部因素对甲状腺产生有害作用时，防止广泛的氧化损伤。因此，氧化损伤以及包括褪黑素在内的抗氧化剂的保护作用可能在甲状腺的生理和病理过程中都发生，然而，这一假设需要进一步研究。
