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  • What’s the first thing that comes to mind when I say the word hormone?

  • Pimples?

  • Mood swings?

  • Cramps?

  • Really inopportune moments where your armpits get sweaty?

  • Are we good?

  • Were good.

  • Hormones are obviously involved in puberty, but theyre so much more than that.

  • Like hormones are involved in how we deal with stress, and in triggering our immune

  • systems, and in steroids.

  • So, grab your antiperspirant and acne cream, today were talking about hormones.

  • In a previous episode you heard me talk about blood and all the stuff floating around in

  • it.

  • We talked about blood cells and glucose and different biomarkers, but I also mentioned

  • chemicals called hormones.

  • Now, I’m assuming that when I say the word hormones, youve already heard about testosterone

  • and estrogen, but hormones are a much more diverse part of our physiology than just those

  • two.

  • Hormones are any number of chemical messengers that get secreted by glands, travel through

  • the bloodstream, and have an effect on cells with receptors for that hormone all around

  • the body.

  • Theyre like a long distance messaging service in one of our body’s systems called the

  • endocrine system, a system for communicating messages across long distances in our bodies.

  • And their effects are incredibly diverse as well.

  • Hormones can stimulate growth, metabolism, immune function and much more.

  • Some hormones even double, triple, or quadruple dip in the functions around your body.

  • For example, thyroid hormone is important for development while youre in utero, but

  • also in maintaining metabolism in your adult body.

  • At the same time, multiple hormones can team up to do the same job.

  • Like controlling blood sugar largely depends on the hormone insulin which is made by your

  • pancreas.

  • But it also depends on hormones like glucagon, cortisol, epinephrine, and growth hormone.

  • The point is, it’s really hard to imagine the endocrine system as a single cause and

  • a single effect.

  • Hormones are less linear, and more like a tangly web.

  • That’s in part because this system is built off of feedback loops, mechanisms where changing

  • one aspect of the loop can lead to increases or decreases of another depending on the situation.

  • These feedback loops can be positive or negative, which doesn’t mean good or bad, just how

  • a hormone is affected by some other substance.

  • In a positive feedback loop, if you increase one factor, it also increases another which

  • increases the original factor which keeps the loop going.

  • To quote a late nineties chip advertisement, once you pop the fun don’t stop.

  • Right, let’s take a look at childbirth.

  • Now that I say that out loud I’m not sure it was the best transition line, but let’s

  • roll with it.

  • During childbirth, the size of the baby’s body applies pressure to the cervix it’s

  • trying to pass through.

  • This triggers the release of the hormone oxytocin which stimulates more cervical contractions

  • which stimulates more oxytocin which stimulates more contractions and so on.

  • We don’t use positive feedback loops as often as negative feedback loops since they

  • can end up with hormone levels spiraling way past the normal, ideal value.

  • But in this case, the feedback loop has a natural stopping point when the baby is born.

  • Then afterwards, the oxytocin levels return to what they were before childbirth.

  • Way more commonly, our hormones are regulated by negative feedback loops, where an increase

  • in one substance eventually eventually leads to a decrease of that same substance.

  • This makes sure hormone levels stay fairly consistent from day to day.

  • For example, your body can sense when your blood is dehydrated and itll adjust some

  • hormones so you can conserve as much water as possible.

  • One of those involves increasing the release of vasopressin, a hormone released by the

  • pituitary gland.

  • This bump in vasopressin makes the kidneys more permeable to water by temporarily adding

  • little water channels onto the surface of cells.

  • This moves water back into the bloodstream towards a more normal value.

  • And now that the blood is back to normal, the pituitary stops pumping out as much vasopressin.

  • That’s what makes this a negative feedback loop.

  • Vasopressin increased, it had its effect, so the body lowers its secretion.

  • One of the other hormones that uses a negative feedback loop is cortisol, arguably one of

  • the most important hormones, and an example of a steroid, which well come back to.

  • Cortisol is often called the stress hormone since it gets released during times of stress

  • and gives our bodies resources for surviving the stressor like increasing sugar metabolism

  • and buffing up our immune system.

  • This hormone is constantly in the process of its feedback loop since, as you know from

  • existing as a human in the modern world, life is stressful.

  • So our bodies are constantly pumping out cortisol, which begs the question, how do we make a

  • hormone?

  • Well what theyre made of differs from hormone to hormone.

  • Most are made of proteins, or peptides, some from phospholipids, while some are made out

  • of cholesterol.

  • And our buddy cortisol is made out of cholesterol.

  • That’s part of what makes it a steroid, hence thestero-” part of both words.

  • In order for cholesterol to turn into any steroid, it goes through a transformation

  • pathway .. It starts by converting into a molecule called

  • pregnenolone.

  • From there it can convert into progesterone, an important hormone in pregnancy and the

  • ovulation cycle.

  • Even if you personally don’t ovulate, progesterone still makes important compounds in your body.

  • And with a few more chemical conversions it can turn into cortisol, or into androgens,

  • which include testosterone or estrogen.

  • Testosterone itself can then get converted into estradiol, a super common estrogen.

  • By the way, that was so fascinating to me when I first learned it.

  • When I was in primary school, I was taught that testosterone and estrogen were opposites,

  • but in fact, theyre extremely similar chemically and get made from the same ingredients.

  • So when were talking about steroids, were talking about hormones derived from cholesterol.

  • But in everyday conversation, when people talk about steroids, theyre probably talking

  • about anabolic steroids, hormones taken for the purpose of building big strong muscles.

  • These work by slipping into muscle cells, and hooking up to an androgen receptor.

  • This stimulates the cell to produce more proteins and thus bigger muscles.

  • Now, just because these types of steroids have been abused in the past doesn’t mean

  • that the broader class of steroid hormones themselves are harmfulin fact, doctors

  • often prescribe steroids as a medication.

  • Most of the time, these medications have nothing to do with muscle.

  • Take a group of hormones called corticosteroids.

  • The etymology gives this one away, but these are any steroids that resemble cortisol.

  • These hormones have a /bunch/ of different effects from controlling the stress response

  • to regulating our immune system.

  • Now, I want to be super clear.

  • Corticosteroids aren’t immune cells, theyre chemicals that can have an immune effect.

  • What makes them so effective is their ability to switch off multiple genes involved in different

  • aspects of inflammation.

  • Let’s break that down.

  • Inflammation is what happens when our bodies mount an immune response, and part of that

  • is making certain proteins.

  • These proteins aren’t just the ones that go into building muscles, but include enzymes

  • for speeding up chemical reactions or different chemical messengers involved in recruiting

  • immune cells.

  • Now, our genes hold all the information needed to manufacture these proteins.

  • And certain chemicals called transcription factors can get our cells to crank out more

  • and more of those inflammatory proteins.

  • So when corticosteroids are floating around in our blood and make their way into a cell,

  • they start a process that inhibits the effect of those transcription factors that keep inflammation

  • going.

  • Plus in larger doses they can stimulate the production of anti-inflammatory proteins.

  • And because of that, these steroids are also a useful treatment for reducing inflammation

  • in conditions like arthritis or allergies.

  • That long-acting asthma inhaler?

  • Yep, that’s a steroid to reduce inflammation in your lungs.

  • One of their other biggest use cases is acting as an immunosuppressant, literally a drug

  • that intentionally weakens your immune system.

  • Wait, why would you weaken your immune system on purpose?

  • Well, most of the time the immune system is good at identifying the things we don’t

  • want in our bodies and getting rid of them.

  • But sometimes, our immune systems turn on us and attack our own tissues.

  • For instance, if you watched our other series Sick, youve heard us talk about lupus,

  • an autoimmune disease that can cause inflammation.

  • One of the consequences of that disease could be kidney inflammation, and if it gets bad

  • enough it might lead to kidney failure, which is lethal.

  • The steroid comes in handy by slowing down the production of chemicals that lead to inflammation,

  • and by tweaking how white blood cells work.

  • A doctor might prescribe an immunosuppressant steroid to someone with lupus to reduce inflammation

  • and save their kidney and thus life.

  • So it’s a trade off.

  • Increase your risk of infections from the outside world but save yourself from your

  • own body.

  • You might also need to weaken your immune system after getting an organ transplant.

  • According to your body, that new organ is a foreign object and shouldn’t be there.

  • Well learn all about how different cells in the body communicate with each other, including

  • some of those immune cells, in the next episode.

  • Thanks for watching Human on Seeker.

  • I'm Patrick Kelly.

What’s the first thing that comes to mind when I say the word hormone?

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為什麼我們需要荷爾蒙? (Why Do We Need Hormones?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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