雌激素

let's talk about one of the major female sex hormones estrogen and before we officially start I should mention that even though I said estrogen is one of the major female sex hormones I just want to be clear here that males also produce and need a bit of estrogen as well but we just produce sort of a small fraction of what females need and produce so let's take a look estrogen is produced in females primarily by the ovaries and as sort of a bonus when she's pregnant her placenta also produces semestre known as well there's also a little bit made by the adrenal glands that sit on top of the kidneys the breasts and by fat cells in general but we'll sort of keep our focus on the ovaries as the primary source for now so the anterior pituitary hormone called follicle stimulating hormone or FSH causes follicles in the ovaries to develop and when follicles in the ovaries develop two groups of cells within them called theca cells and granulosa cells start to sort of team up and release estrogen into the bloodstream and the amount sort of goes up and down throughout each month and and that's because of signals from the hypothalamus and the anterior pituitary so now we know where we get most of the estrogen in the body and we know that it's levels are regulated by interactions between the brain and the ovaries but before we talk about what it does from a biological standpoint I want to go over how estrogen actually works so after estrogen is made in the ovaries by these granulosa cells it's transported to other places in the body by the bloodstream and so I'll just draw little red blood cells here and then I'll draw estrogen and light purple here and these blood vessels take the estrogen all over the body so it can carry out all of its all of its biological functions but once it gets to its target what exactly happens how exactly does it work so to show you this I'll blow up a cell here in the thigh and let's say that this here is the cell membrane and this purpley blue thing here is the the blood vessel that's sort of lining or running beside that cell so we'll draw in our red blood cells and our estrogen so when estrogen sees a cell that it wants to enter it crosses the cell membrane where it's picked up by a carrier protein and I'll draw that as a taxi because all it's really doing is picking up estrogen and transporting it to its next destination in the cell which is the nucleus and the nucleus is where our DNA is and so estrogen works by binding near to certain genes to change their expression and so that'll ultimately change the behavior of that target cell so that's how it works but what exactly does it do in the body what sort of effect does it have on a person's body and I purposely say a person's body here to remind you that males and females sort of depend on estrogen to do different things in our respective bodies so for example in males specifically estrogen has a role in the maturation of sperm and is stored to sort of pair up with testosterone to to increase libido also known as as the sex drive but estrogen does a lot of female specific stuff it actually has a lot to do with the growth and the development of the female reproductive tract so for one we know that it stimulates the growth of the ovaries and the follicles inside the ovaries as part of the reproductive cycle it also causes growth of the smooth muscle components of the female reproductive tract for example the smooth muscle in the uterus and the uterine tubes after puberty it also stimulates the growth of the female's external genitalia and breasts during puberty as well and and the way it sort of manages breast growth is by primarily increasing the the fat that gets deposited in the breasts and speaking of fat deposition estrogen is also responsible for the so called female fat distribution pattern which is deposition on the hips as well as the breasts in contrast to the male pattern which is fat distribution around the tummy so those are the major effects that estrogen has on the reproductive tract and and on that fat distribution role there is some other really important non reproductive roles that estrogen has as well and we'll touch on two of those so number one estrogen does some really good things for your blood cholesterol levels and for you to really appreciate this point I kind of have to tell you a bit about cholesterol first so bear with me for a minute and let's have a quick chat about Co so cholesterol is a lipid molecule that despite all the negative press it receives it's kind of essential for life it's required to make nice healthy cell membranes and maybe a bit ironically we make a lot of our hormones out of cholesterol and in fact our testosterone and estrogen themselves are made from cholesterol our cholesterol has to be carried around our bodies in the bloodstream and essentially we have a couple types of molecules that that carry the cholesterol around so we have one molecule called HDL or high density lipoprotein and we have another molecule called LDL or a low-density lipoprotein and all that density business and their names just refers to the to the ratio of protein to cholesterol that these molecules have in them so for example HDL has lots of protein and a little bit of cholesterol so it's high density in terms of its protein content but for simplicity sake we'll just call them good cholesterol being the HDL and bad cholesterol being the LDL and the reason they're differentiated as being quote good and bad is because high levels of the bad kind LDL is implicated in causing problems with your blood vessels which can lead to things like heart attacks or strokes and optimum levels of the good kind HDL is correlated with reduced risk of having these bad things happen so back to estrogen estrogen actually reduces the bad cholesterol LDL and increases the good cholesterol HDL so that's pretty great kind of a lot of cholesterol background to make that point but it's physiologically a really important role of estrogen and in fact after a female slows her production of estrogen in her 50s her levels of HDL can actually start to go down so that's estrogen and cholesterol another really important estrogen role is one that has to do with preserving the strength of our bones in our in our skeletal system so throughout our lives bones are constantly undergoing renovations and that sounds a bit weird right because we always we always tend to think of bones as being these static unchanging things but actually on a microscope epic level they're constantly being broken down and built back up an estrogen actually effects part of that process so estrogen slows down the cells that are involved with the breakdown portion of your bone renovations so as a result of that your skeleton stays more dense for a longer period of time and that means that as estrogen levels get lower when a female gets older she's more at risk for developing a bone condition where the bones get brittle and weak and that's called osteoporosis so that's a little overview of the importance of estrogen and a few of its biological roles within the body