Why are some bodily hormones only produced when we sleep?

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Title asks it all. Cheers 🙂

In: Biology

Not entirely sure, but I know we grow the most when we’re asleep so maybe it’s just that process that pushes the body into hypergrowth.

I think it would be helpful to examine this question as one example of a more general question: Why do bodies produce some hormones under some conditions but not other? And as a follow-up how are they able to do this?

The why question is so easy to answer that it’s not very illuminating: it’s either because natural selection favored organisms that do it this way, or this is the dominant genetic trait and natural selection didn’t strongly disfavor it. Over time, organisms that did it this way survived and, either through selection pressure, or through random chance, reproduced more than organisms that didn’t do it this way and now many organisms do it this way. Slightly more interesting is the gene-level view of things, which is that natural selection favored organisms that contained genes for doing it this way, or that this is the dominant genetic trait and natural selection didn’t strongly disfavor organisms with it. Over time, organisms with these genes survived and, either through selection pressure, or through random chance, reproduced more than organisms without these genes and now these genes have come to dominate the population.

The how it the interesting question though. There are a lot of physical and chemical signals telling cells when to do one thing and when to do another. Some hormones may be produced when gravity pulls sideways at the body and turned off when gravity pulls downward. This could be moderated through the flow of liquids that are affected strongly by gravity such as your blood or your stomach contents. Other hormones could be produced when there is no light present because light exposure on your skin or optic nerve inhibits production. Still others may be produced when your overall metabolic rate is low and chemicals produced during the day are not present or have begun to degrade.

As you can see, it may not be the case that some hormones that are produced when sleeping are produced because of sleeping. They could be, but there are also likely a large number of other environmental factors that are associated with sleep and trigger production.