‘Oestrogen’ actually refers to a group of chemically similar hormones – oestradiol (the most abundant), oestrone, and oestriol.
 
Hormones are vital chemical substances that are often referred to as ‘chemical messengers’ as they carry information and instructions from one group of cells to another.
 
Oestradiol is the main oestrogen made by the ovaries, and it is also the strongest oestrogen. After the menopause, the oestradiol levels drop, and oestrone becomes the main form of oestrogen in the body made in the adrenal glands and fat cells.
 
Beneficial effects:

Oestrogen has the following effects on the body:

• Programmes the breasts and uterus for sexual reproduction
• Controls cholesterol production in ways that limit the build-up of plaque in the coronary arteries
• Preserves bone strength by helping to maintain the proper balance between bone build-up and breakdown.

How Does Oestrogen Work?

Oestrogen circulates in the bloodstream and binds to oestrogen receptors. Such receptors are present in numerous tissues other than those associated with reproduction, including bone, liver, heart and brain. They normally reside in the cell’s nucleus, along with DNA molecules. In the absence of oestrogen these receptors are inactive and have no influence on the DNA. But when oestrogen enters a cell and passes into the nucleus, the oestrogen binds to the receptor, thereby causing the shape of the receptor to change which in turn will influence the cell behaviour.
 
In some target tissues, the main effect is cell proliferation. In breast tissue, for example, oestrogen triggers the proliferation of cells lining the milk glands, thereby preparing the breast to produce milk if the woman should become pregnant.