As a woman gets older, the sensitivity of the ovarian follicles to two hormones, Follicle Stimulating Hormone (FSH) and Lutenizing Hormone (LH), decreases. As a result ovulation is disrupted; many cycles will fail to produce eggs, which in turn results in irregular periods. Ovaries produce less oestrogen and the decline in LH eventually causes a decline in the production of progesterone. Eventually ovaries fail completely to produce oestrogen and women derive their oestrogen entirely from the adrenal glands and fat cells in the form of oestrone.
 
During this period fertility diminishes but a woman will still require contraception until 12 months after her last period. It is also in this period that she may experience menopausal symptoms. This can occur as early age 35, although most women experience them often in their mid to late 40s. The duration of perimenopause can be a few years, ten years or even longer. The actual duration and severity of perimenopause in any individual woman cannot be predicted in advance or during the process.
 
The resultant decreased levels of circulating oestrogen not only affects the reproductive functioning, but also has far ranging effects from brain to skin. The decreased levels of progesterone also have physiological and emotional ramifications.
 
Effects of Oestrogen Reduction
 
In the perimenopause years, many women undergo significant bodily changes resulting from hormonal fluctuation, the obvious one being irregular periods. 
 
There are also many well documented physiological signs of perimenopause – the most common being the "hot flush”. Other common perimenopause symptoms are palpitations, headaches, aches and pains and sleep problems.
 
There are also psychological effects like mood changes/irritability, anxiety, and concentration problems. Some of these complaints may be directly related to the actual hormonal fluctuations but more research is required. However, these can be compounded by stressful situations that tend to happen at this time in a woman’s life, such as society’s negative perceptions of aging, retirement and children leaving home.
 
It is therefore difficult to separate hormonal-related perimenopause symptoms from emotional-related symptoms. In fact they are probably mutually reliant.
 
There are also sexual problems experienced by women in perimenopause, such as vaginal dryness, which may cause pain or discomfort during intercourse as oestrogen reduction decreases the blood supply and gland stimulation to the area, promoting a more alkaline environment that is predisposed to infection. 

What is the menopause?
 
Postmenopause