Melatonin Essay

Melatonin is a naturally occurring hormone in humans that is mainly synthesised in the pineal gland, but can also be formed in other parts of the body, such as the eyes, the GIT, bone marrow, lymphocytes, and skin (Cutando et al., 2012). It is not a ‘traditional’ hormone in the sense that it does not have specific organs that it is synthesised in or that it targets (Cutando et al. 2012). One of the roles of melatonin is its involvement in various regulatory activities, such as the light/dark cycle, core body temperature, and blood pressure.
Melatonin is synthesised and released in darkness, so there are varying levels of melatonin in circulation throughout the day. The suprachiasmatic nucleus, or the biological clock, is the master clock of the mammalian brain and is concerned with circadian rhythms. It is reset on a daily basis by light in the retina during the day and melatonin secretion at night (Glenister et al., 2013).
Melatonin is also an anti-oxidant, as well as having a role to play in immunomodulation.
With its immunomodulatory properties, melatonin can augment lymphocyte infiltration and anti-tumour activity (Glenister et al., 2013). This is because melatonin can easily cross cell membranes, as well as the blood-brain barrier. In animal models, melatonin has also been shown to prevent damage from carcinogens to mitochondrial and nuclear DNA. It appears to be both protective and effective against a variety of cancers, especially sex-hormone driven cancers, including ovarian, breast, endometrial, prostate, and testicular cancers (Bizzarri et al., 2013). This is said to be because melatonin has a soothing effect on reproductive hormones. Melatonin also produces promising results for cervical cancer but more research needs to be done on this
topic.
With regards to the role melatonin plays in cancer treatment, it inhibits cell proliferation, as well as the formation of tumours. The mechanism behind this is an induced suppression of the tumour’s linoleic acid uptake and its metabolism to a mitogen via a melatonin-receptor mediated mechanism that can be found in isolated tissues for both rat hepatoma and human breast cancer xenografts (Saha, Koley & Patra, 2013). A mitogen is a chemical that triggers mitosis. Melatonin also stimulates cell differentiation and apoptosis. Differentiation therapy is an approach in which the malignant cells are stimulated to resume normal processes of maturation and differentiation (Cutando et al., 2012). Cancer chemotherapy drugs are sensitized by melatonin for apoptosis (Bizzarri et al., 2013). Another role melatonin can play is that supplementation during therapy can possibly cause a reduction in dose-limiting toxicity (Rao and Narechania, 2016). However, this requires further research.