Menopause is defined as the state of an absence of menstrual periods for 12 months. The menopausal transition starts with varying menstrual cycle length and ends with the final menstrual period. Perimenopause is a term sometimes used and means "the time around menopause." It is often used to refer to the menopausal transitional period. It is not officially a medical term, but is sometimes used to explain certain aspects of the menopause transition in lay terms. "Postmenopausal" is a term used to as an adjective to refer to the time after menopause has occurred. For example, doctors may speak of a condition that occurs in "postmenopausal women." This refers to women who have already reached menopause.
Menopause is the time in a woman's life when the function of the ovaries ceases and she can no longer become pregnant. The ovary (female gonad), is one of a pair of reproductive glands in women. They are located in the pelvis, one on each side of the uterus. Each ovary is about the size and shape of an almond. The ovaries produce eggs (ova) and female hormones such as estrogen. During each monthly menstrual cycle, an egg is released from one ovary. The egg travels from the ovary through a Fallopian tube to the uterus.
The ovaries are the main source of female hormones, which control the development of female body characteristics such as the breasts, body shape, and body hair. The hormones also regulate the menstrual cycle and pregnancy. Estrogens also protect the bone. Therefore, a woman can develop osteoporosis (thinning of bone) later in life when her ovaries do not produce adequate estrogen.
The average age of menopause is 51 years old. But there is no way to predict when an individual woman will have menopause or begin having symptoms suggestive of menopause. The age at which a woman starts having menstrual periods is also not related to the age of menopause onset. Most women reach menopause between the ages of 45 and 55, but menopause may occur as earlier as ages 30s or 40s, or may not occur until a woman reaches her 60s. As a rough "rule of thumb," women tend to undergo menopause at an age similar to that of their mothers. Perimenopause, often accompanied by irregularities in the menstrual cycle along with the typical symptoms of early menopause, can begin up to 10 years prior to the last menstrual period.
Menopause is a point in time and not a process- it is the time point in at which a woman’s last period ends. Of course, a woman will not know when that time point has occurred until she has been 12 consecutive months without a period. The symptoms of menopause, on the other hand, may begin years before the actual menopause occurs and may persist for some years afterward as well.