If you any active chemical in your system that alters the homoestasis, why does this chemical eventually leave the body? What prevents it from staying in the body forever?
In: Biology
There are some good answers on here already, but I thought I’d try my hand at summarizing and adding a bit more detail where I could.
As was already mentioned, nothing in the body , natural or not, really “lasts forever.” Everything gets broken down or excreted at some point for some reason like:
* it’s in the wrong body/organ/cell/compartment
* it served its function and needs to be thrown out/recycled
* it’s “old”
* there’s too much of it around
* it’s “labelled as foreign”, etc
And it’s really important for our bodies to have a constant turnover of contents for the sake of maintaining homeostasis like others have mentioned. Usually, it’s detrimental for the body to hold onto too much of anything, even “natural” things. For example, there’s something called haemachromatosis where a person has too much iron in their bodies, which can cause problems. Too much copper can deposit pigmented rings in your eyes and cause other health problems. Same principle applies to just about every other chemical, mineral, fat, protein, etc. Other thing too is that a lot of our body lives in a constant state of simultaneous “break down and building.” For example, in your bones this process is called “remodelling” and helps strengthen them in response to the day-to-day stress you put on them.
As for the second part of your question, how the body knows and gets rid of stuff is a whole field unto itself, and involves a bunch of really cool mechanisms and reactions that our body uses. In short, every cell in your body has some capacity to break down, tag, and/or excrete everything from proteins to chemicals. While your liver and kidneys do the bulk of the heavy lifting, all processes generally involve some combination of:
* breaking down the substance outright or
* chemically reacting on or with the substance to make it easier to dissolve in water (so it’s easier to pass into urine). There are some things in the body that are tagged to make it dissolve more easily in fat to be passed into stool, but that’s a whole other thing
Hope that helps!
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