One of the most highly conserved features of vertebrate physiology is a robust daily rhythm in melatonin synthesis by the pineal gland. This in turn controls the daily rhythm in circulating melatonin, characterized by high values occurring at night. This high-at-night pattern is seen in all animals, independent of lifestyles. This signal has broad effects on biological processes, as documented in over 10,000 publications since the discovery of melatonin in the late 1950s by Aaron Lerner, the father of the melatonin field. One interesting aspect of melatonin is that it does not have a specific, wellconserved effect on a single-target process, as is the case for other hormones, e.g., growth hormone and insulin. Rather, melatonin is a circulating time signal that is interpreted and used differently by different species to optimally entrain their physiology to the environment. This has been reviewed by many experts in the field and is beyond the scope of this chapter. Rather, this chapter will focus on a less well-studied facet of melatonin, which is how the daily rhythm in melatonin is regulated.
Ganguly, S., & Klein, D. C. (2017). The Timezyme and Melatonin: Essential elements of vertebrate timekeeping. In Biological Timekeeping: Clocks, Rhythms and Behaviour (pp. 503–520). Springer (India) Private Ltd. https://doi.org/10.1007/978-81-322-3688-7_24