As part of the menstrual cycle, the ovaries produce oestrogen and progesterone. They also produce androgens, which include testosterone. Hormone levels usually begin to change around the age of 40 and the perimenopause (the years just before menopause) is usually between 50 and 55. As hormone levels start fluctuating quite dramatically during perimenopause, women begin to have symptoms such as hot flushes, vaginal dryness, irregular periods and insomnia.
These hormonal changes are due to the ageing ovaries losing their ability to produce eggs and hormones. At this time, during the monthly cycle, women will have widely varying oestrogen levels as the ovaries continue to try to produce eggs. Often there will be cycles in which no ovulation occurs and no progesterone is produced. As a woman approaches menopause this can lead to irregular menstrual cycles with heavy or abnormal bleeding.
At this point, the ovaries stop producing and releasing eggs (ovulating) each month and periods cease. The ovaries are no longer producing estradiol and progesterone (although they may continue to produce androgens). Menopause does not mean that there is no oestrogen in the body anymore. Women with more body fat will usually have more oestrogen than thinner women, because oestrogen is aromatised in fatty tissue. After menopause, there is much less oestrogen and testosterone in the body than before menopause, and very little progesterone.
This drop in hormone levels can have various effects, including the familiar symptoms of menopause such as:
Loss of libido.
A woman who has surgical menopause, in which her ovaries are removed (usually along with her uterus and fallopian tubes), will have a sudden drop in all sex hormone levels.
This sudden loss of hormones can cause severe symptoms and health problems, especially in younger women, unless adequate hormone replacement is provided.