Hormones are the solution to everything! The newspapers say cortisol kills and melatonin makes you sleep. But what are hormones actually? And what do they do?
Yes indeed, you need to keep your hormones in order or else you will die. This statement is partially true and headlines like this have sold many newspapers in the last decade. We still need to emphasise the partially-true aspect of these statements. First lesson, hormones are complex. Spoiler alert. The main point of this article has been revealed. It’s like one of those movies where the starting scene gives you a glimpse of the final scene and thereafter takes you back to the beginning. Ok, let us get back to the beginning then.
Hormones are chemicals circulating in the blood all around your body. They are sometimes referred to as messages to the organs and tissues. Here we have our first misconception. This analogy opens for the interpretation that the organs will actively consider their actions as a reader and decision maker of hormone messages. Therefore, we need to refer to hormones as signals. Signals are simpler. It’s like a red or green traffic light. Every organ knows how to respond to the specific signal of the specific hormone. The same hormone could, however, initiate different actions in different organs. Like a master key fits many keyholes and could initiate different actions. A green signaling light to the heart could be a red-light signal to the digestive system.
Cortisol – The Source of Evil
Get rid of it or it will kill you. I can assure you, it’s the other way around. You cannot live without your cortisol. This hormone is a central player in the regulation of homeostasis. When challenged, you need to get your cortisol levels up in order to sufficiently respond to the task at hand. Thereafter, the levels of cortisol will get back to normal, which is the pattern of a healthy person’s hormone balance. Addison’s disease is one example of when cortisol production is insufficient. This life-threatening condition involves treatment of hormones in order to get cortisol levels back to a normal rate (1)Svetlana Ten, Maria New, Noel Maclaren, Addison’s Disease 2001, The Journal of Clinical Endocrinology & Metabolism, Volume 86, Issue 7, 1 July 2001, Pages 2909–2922, https://doi.org/10.1210/jcem.86.7.7636.
When cortisol is assessed in research, we often interpret heightened levels as an indicator of stress. In such research there are several points to consider. If the researcher wants to observe high cortisol levels one could simply do the collection of samples in the morning, preferably 30 minutes after the individuals normal wakeup time. This is due to the circadian rhythm of cortisol. (2)Eva Fries, Lucia Dettenborn, Clemens Kirschbaum, The cortisol awakening response (CAR): Facts and future directions, International Journal of Psychophysiology, Volume 72, Issue 1, 2009, Pages 67-73, ISSN 0167-8760, https://doi.org/10.1016/j.ijpsycho.2008.03.014. Do you need your participant to have low cortisol levels, you should measure the levels in the evening. The cortisol is then at the lowest point in the daily fluctuation. Here you see how time of day can have a major impact on hormone measurements used for research, or reported in newspapers.
Melatonin – The Sleep Hormone
You probably start to get the format of this article now. So, melatonin does not measure sleep then? Studies of the melatonin rhythm in humans show an increase of melatonin in the evening and it seems to correlate well with the feeling of sleepiness. The same increase is seen when assessing melatonin in rats (3)Reiter R. J. (1993). The melatonin rhythm: both a clock and a calendar. Experientia, 49(8), 654–664. https://doi.org/10.1007/BF01923947. This is where the sleep researchers got their «melatonin equals sleep-hypothesis» falsified. Rats are night-active animals (nocturnal), meaning they do not sleep at night. Melatonin is in consequence a hormone which signals time of day. For humans this is the time we like to sleep and for rats this is the time they like to get active. In research, the method of “dim light melatonin onset” is widely used to measure our internal day-night rhythm (4)Pandi-Perumal, S. R., Smits, M., Spence, W., Srinivasan, V., Cardinali, D. P., Lowe, A. D., & Kayumov, L. (2007). Dim light melatonin onset (DLMO): a tool for the analysis of circadian phase in human sleep and chronobiological disorders. Progress in neuro-psychopharmacology & biological psychiatry, 31(1), 1–11. https://doi.org/10.1016/j.pnpbp.2006.06.020. In this procedure one usually collects saliva samples in the evening to pinpoint at which time melatonin levels rise. This is perhaps the reason why popular media often assign melatonin as a sleep hormone.
The body is a delicate system. Hormones play their part in the ever changing environment of our internal communication system. Blood flows around at all times and delivers a variety of hormonal signals. Sometimes these signals don’t even use the bloodstream as transportation (5)Rajaram RD, Brisken C. Paracrine signaling by progesterone. Molecular and Cellular Endocrinology. 2012 Jun;357(1-2):80-90. DOI: 10.1016/j.mce.2011.09.018..
As this brief article is getting to its end, you are starting to understand the glimpse you got from the spoiler in the beginning. Now, the reference list rolls over the screen as movie credits and I leave you to reflect on the moral of this story while the main character does an advanced yoga pose on the top of a mountain, trying to get rid of his cortisol.