Heath and Aging

Menopause: Time for a Change

An Introduction to Menopause

Menopause, also known as "the change” or “change of life,” is a normal part of a woman’s life. It is a point in time—the last menstrual cycle, the last period. The years leading up to that last period, when women might be experiencing menopausal symptoms like changes in their monthly cycles or hot flashes, are called the menopausal transition. It is a common mistake to use the word menopause to describe this whole transition.

The menopausal transition occurs at a time in a woman’s reproductive life when the production of estrogen and progesterone, two hormones made by the ovaries, may vary dramatically and unpredictably. The ovaries are two small glands found on either side of the top of the uterus or womb. Before menopause, they hold eggs, one or more of which are released during a menstrual cycle. If the egg then joins with sperm following sexual intercourse and attaches itself inside the uterus, pregnancy is the result. Ovaries also produce chemical substances known as hormones, which travel through the blood to other tissues to control how cells work. One of these, estrogen, has effects on cells in many parts of the body including the reproductive organs, brain, heart and blood vessels, and bone.

woman with a bushel of applesUsually in her forties, a woman’s body starts changing. Some differences, such as a thickening waist, can happen because she is getting older, but others, like vaginal dryness, are caused by changes in her hormone levels. As a woman ages and especially as she gets closer to menopause, her ovaries get smaller. This time of changes in hormone levels and menstrual cycles is called the menopausal transition. You might also hear it called perimenopause. It usually lasts several years until 12 months after your last period. Once a woman has gone a full 12 months without a period, she can be fairly sure that she has been through menopause and is now in postmenopause. The chart below shows how the patterns of hormone production change as women go from their reproductive years through the menopausal transition to postmenopause. Postmenopause lasts the rest of a woman’s life.

Going through menopause is a little like driving on an unfamiliar, twisting road with an unclear destination. You may not be sure of all that is happening, where you are going, or what’s coming next. In fact, you won’t realize you have reached your destination (menopause) until you are past it and see it in your rearview mirror.

The average age of menopause is 51. That means that almost half of all women have their last period and reach menopause before that age, and some women may not have even started perimenopause yet.

It’s not easy to know when you are in the menopausal transition. Menopausal symptoms, along with a physical examination, medical history, and maybe some blood tests, may provide useful clues. But, it is not possible to correctly predict when a woman’s final period will be. Your doctor could test the amount of estrogen in your blood or the level of FSH (follicle-stimulating hormone), another hormone that changes at this time. But, levels of both estrogen and FSH normally go up and down during your menstrual cycle. So, these test results alone cannot be used to predict or confirm menopause.

Levels of two other female hormones, progesterone and luteinizing hormone (LH), also rise and fall during your menstrual cycle. Progesterone levels drop after menopause, and LH levels go up (see chart below).

Even though your monthly periods are not regular anymore, you can get pregnant during the menopausal transition. In fact, the irregular periods common in menopause make it harder to predict when an ovary is releasing an egg, the time when sexual intercourse is most likely to result in a pregnancy.

Do not assume that a couple of missed periods mean you are beginning the menopausal transition. Check with your doctor to see if you are pregnant or if there is another medical cause for your missed periods.

  This figure presents three line graphs, each showing changes in a woman's levels of estrogen, progesterone, FSH (follicle-stimulating hormone), and LH (luteinizing hormone) over six months. There are no units on any of the axes of the line graphs. The first line graph, titled 'Premenopause (180 days),' shows fluctuating levels of the four hormones over the six months. The line for LH rises to six sharp peaks, which are the highest peaks on the graph. The line for progesterone rises to six rounded peaks, which are just over half the height of those shown for LH, to the right of the rises in LH. The line for estrogen rises six times to approximately the same level as progesterone, with a dip and second rise within each peak before dropping down to the original level. The line for FSH rises and falls slightly approximately 12 times over the 180 days. The second line graph, titled 'Perimenopause (180 days),' shows randomly fluctuating levels of all four hormones. The lines for estrogen and FSH rise to the highest levels and fluctuate the most. The lines for progesterone and LH fluctuate less and overall rise to lower levels than those for estrogen and FSH. The third line graph, titled 'Postmenopause (180 days),' shows nearly horizontal lines for all four hormones, illustrating nearly consistent levels of each of the four hormones. The line for progesterone is at the lowest level, and the line for estrogen is slightly above that for progesterone. The line for FSH is the highest. The line for LH is approximately one-third of the way between estrogen and FSH.
  Changes in Hormone Level Patterns Over Six Months (click to view)

At any age before natural menopause, an operation to remove both ovaries or the uterus results in “surgical menopause.” The medical term for the operation is a hysterectomy (surgery to remove the uterus) or bilateral oophorectomy (surgery to remove both ovaries). Removing either both ovaries or the uterus stops monthly periods right away. If the surgeon removes the uterus but is able to leave one or both ovaries, estrogen and progesterone might still continue to be made for a while longer. However, research suggests that, after a hysterectomy, the ovaries may stop making these hormones sooner than might normally be expected.

A woman who has either a hysterectomy or both ovaries removed often faces more intense menopausal symptoms than a woman who reaches menopause naturally. Removing both ovaries abruptly cuts off hormone production. If you are having this surgery, discuss how to manage your symptoms with your doctor before your operation. Without treatment, symptoms may begin soon after surgery. Surgical menopause also puts you at early risk for bone loss and heart disease. Stay in touch with your doctor as you recover.

Usually menopause happens naturally, but some women develop symptoms of menopause and stop having menstrual cycles much earlier than expected. Before age 40, a menopause-like condition can happen for no known reason, or it can be caused by radiation treatment, some medicines like those used in chemotherapy, an autoimmunity (some of a woman’s own body cells attacking her ovary or ovaries), or genetic errors. Radiation can make your ovaries stop working, as can some treatments like chemotherapy for cancer.

In the past when menopausal symptoms developed before age 40, it was referred to as “premature menopause.” However, the term “premature menopause” is no longer considered scientifically accurate. That’s because some women with this condition have ovaries that produce hormones irregularly and a return of menstrual periods, and some can even become pregnant after the diagnosis. The terms “premature ovarian failure” or “primary ovarian insufficiency” are now used to describe this condition. Women with this problem may experience symptoms of menopause like hot flashes and vaginal dryness.

  Reproductive Years Menopausal Transition Postmenopause
Average Age* First Period:
16-30 31-42 Early transition
Late transition
late 40s,
early 50s
Final Period: 51 50s
and beyond
Menstrual Cycles Variable Regular Regular Lengths of cycles
vary increasingly
2 or more
skipped periods
No period** No periods
Signs and Symptoms     Fertility
  Hot flashes,
and sleep
Bone loss
as previous

Vaginal dryness, bone loss. Hot flashes can persist. For a few women, hot flashes continue into their 60s and 70s.

*These are average ages. Women vary a great deal in the age at which they go through each of these stages.
**Menopause is said to have occurred after twelve months without a period.

Copyright © 2007 by the American Society for Reproductive Medicine. All rights reserved. No part of this presentation may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system without permission in writing from the American Society for Reproductive Medicine, 1209 Montgomery Highway, Birmingham, AL 35216.

Publication Date: August 2010
Page Last Updated: April 27, 2017