HonCode

Go Back   HER2 Support Group Forums > Articles of Interest
Register Gallery FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
Old 05-21-2014, 07:59 AM   #1
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Post What are Estrogens? National Cancer Institute information

Slide 1

What Are Estrogens?

Next Section >
Estrogens are a family of related molecules that stimulate the development and maintenance of female characteristics and sexual reproduction.
The natural estrogens produced by women are steroid molecules, which means that they are derived from a particular type of molecular skeleton containing four rings of carbon atoms, giving the shape shown here. The most prevalent forms of human estrogen are estradiol and estrone. Both are produced and secreted by the ovaries, although estrone is also made in the adrenal glands and other organs.
'lizbeth is offline   Reply With Quote
Old 05-21-2014, 08:00 AM   #2
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Re: What are Estrogens? National Cancer Institute information

Slide 2

Estrogen Targets Tissue

Next Section >
Estrogens are hormones, which means that they function as signaling molecules. A signaling molecule exerts its effects by traveling through the bloodstream and interacting with cells in a variety of target tissues.
The breast and the uterus, which play central roles in sexual reproduction, are two of the main targets of estrogen. In addition, estrogen molecules act on the brain, bone, liver, and heart.
'lizbeth is offline   Reply With Quote
Old 05-21-2014, 08:01 AM   #3
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Re: What are Estrogens? National Cancer Institute information

Slide 3

Estrogen Receptors

Next Section >
Estrogens act on target tissues by binding to parts of cells called estrogen receptors.
An estrogen receptor is a protein molecule found inside those cells that are targets for estrogen action. Estrogen receptors contain a specific site to which only estrogens (or closely related molecules) can bind.
The target tissues affected by estrogen molecules all contain estrogen receptors; other organs and tissues in the body do not. Therefore, when estrogen molecules circulate in the bloodstream and move throughout the body, they exert effects only on cells that contain estrogen receptors.
'lizbeth is offline   Reply With Quote
Old 05-21-2014, 08:03 AM   #4
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Re: What are Estrogens? National Cancer Institute information

Slide 4

Estrogen Receptors Trigger Gene Activation

Next Section >
Estrogen receptors normally reside in the cell’s nucleus, along with DNA molecules.
In the absence of estrogen molecules, these estrogen receptors are inactive and have no influence on DNA (which contains the cell’s genes). But when an estrogen molecule enters a cell and passes into the nucleus, the estrogen binds to its receptor, thereby causing the shape of the receptor to change. This estrogen-receptor complex then binds to specific DNA sites, called estrogen response elements, which are located near genes that are controlled by estrogen.
After it has become attached to estrogen response elements in DNA, this estrogen-receptor complex binds to coactivator proteins and more nearby genes become active. The active genes produce molecules of messenger RNA, which guide the synthesis of specific proteins. These proteins can then influence cell behavior in different ways, depending on the cell type involved.
'lizbeth is offline   Reply With Quote
Old 05-21-2014, 08:04 AM   #5
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Re: What are Estrogens? National Cancer Institute information

Slide 5

Estrogen-Induced Changes in Cell Behavior

Next Section >
In liver cells, for example, estrogen alters the production of proteins that influence cholesterol levels in the blood.
Cholesterol does not readily dissolve in blood, so before it can be transported through the body, it first becomes bound to special cholesterol-carrying proteins called lipoproteins. The liver produces two such lipoproteins, called low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL-cholesterol is considered to be the “bad” form of cholesterol because it tends to release cholesterol directly onto the inner wall of arteries, creating the “plaque” that can lead to heart disease. In contrast, HDL is considered to be the “good” form of cholesterol because it inhibits the formation of plaque and carries cholesterol away from the arteries and back to the liver.
The net effect of estrogen’s action on liver cells is to increase the amount of HDL cholesterol and to decrease the amount of LDL cholesterol. By increasing HDL and decreasing LDL, estrogen helps to lower the risk of heart disease.
'lizbeth is offline   Reply With Quote
Old 05-21-2014, 08:06 AM   #6
'lizbeth
Senior Member
 
'lizbeth's Avatar
 
Join Date: Apr 2008
Location: Sunny San Diego
Posts: 2,214
Re: What are Estrogens? National Cancer Institute information







Slide 6

Estrogen-Induced Stimulation of Cell Proliferation

Next Section >
In some target tissues, the main effect of estrogen is to cause cells to grow and divide, a process called cell proliferation.
In breast tissue, for example, estrogen triggers the proliferation of cells lining the milk glands, thereby preparing the breast to produce milk if the woman should become pregnant.
Estrogen also promotes proliferation of the cells that form the inner lining, or endometrium, of the uterus, thereby preparing the uterus for possible implantation of an embryo. During a normal menstrual cycle, estrogen levels fall dramatically at the end of each cycle if pregnancy does not occur. As a result, the endometrium disintegrates and is shed from the uterus and vagina in a bleeding process called menstruation.
'lizbeth is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -7. The time now is 10:25 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright HER2 Support Group 2007 - 2021
free webpage hit counter