Biology of Perimenopause

Dr. Susan Love's Menopause and Hormone Book: Making Informed Choices
by Susan M. Love, M.D., Karen Lindsey

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Now you've left puberty, and you're in your fertile years. Here's basically what goes on for the next three decades. Stimulated by FSH, the follicles (the eggs encased in their little sacs) produce estrogen. When estrogen rises to a certain level, the hypothalamus gets the message and secretes LH-releasing hormone, which tells the pituitary to turn off the FSH and produce a surge of LH. When the LH is at its peak, you ovulate-that is, your body releases an egg from the follicle. The follicle shifts to a new phase (the corpus luteum) and starts to produce progesterone in addition to estrogen. These hormones build up the lining of the uterus. The corpus luteum is short-lived, and its production of hormones soon begins to decline. Once the progesterone in your blood drops to a certain level, you get rid of the uterine lining by getting your period. In addition, these lower levels of estrogen and progesterone tell the hypothalamus to get some FSH going, and the cycle continues. Every month (except for those few months when you're pregnant), your body goes through this familiar dance.

It can take a while for this dance of hormones to get its choreography down (Figure 1.2). One study confirmed that earlier on, girls have longer periods. The follicles don't mature, and there may be a longer time between periods. This seems to be in part because the ovaries aren't yet really producing eggs, and egg production is necessary for a regular "loop" to be completed. Once the whole system gets coordinated, a girl's cycles become regular and her symptoms settle.

This dance, like most dances, has a few variations. In some months, you don't ovulate. Then there's no progesterone, and your period may actually come early and be lighter or later, or you may skip a period altogether. Your body also requires a certain amount of fat to ovulate; if you're very thin or anorexic, or an athlete who is very muscular with very little fat, you will often lose your period and in essence be in temporary menopause. This time it is literally a "pause," because you'll get your periods back once your fat level increases.

So far, so good. But our understanding of the process gets a little fuzzier when you come to the end of your fertile years. The standard line in the textbooks is that when you run out of eggs and you're no longer ovulating, your body stops making estrogen. This causes your FSH to go up as your pituitary tries to kick start the ovary into producing more eggs. When that doesn't work, everything just shuts down.

Yet often the symptoms of perimenopause (breast tenderness, headaches, increased vaginal lubrication) are symptoms not of low estrogen but rather of high estrogen. Some recent studies have looked more deeply into what may explain this phenomenon. A study in 1989 followed five perimenopausal women, one of whom had occasional periods every six weeks. Fortunately, the researchers were monitoring her while this was going on. They discovered that she had low estrogen in the beginning of her cycle. Her ovaries were just tired. As a result of the low estrogen, she had symptoms such as hot flashes for a couple of weeks. Meanwhile, her hypothalamus and pituitary responded to these low levels by increasing her FSH. Her ovaries woke up in a panic, as though they had been sleeping on the job, and decided to make up for their inattention by sending out lots more estrogen-two to three times the normal amount. And then she ovulated. Now her symptoms were those of high estrogen-breast tenderness, etc. Her progesterone went up after ovulation and her period came exactly two weeks late and was very heavy, because of the extra estrogen. You can see why life at this stage is so unpredictable. (While working on this book, I experienced exactly the same cycle as the woman in the study and was relieved to know exactly what was going on.)

This is often what happens in perimenopause. Sometimes your estrogen levels are high and your progesterone is low, and you might get symptoms of PMS. At other times, your estrogen levels shift and you get hot flashes. Then for several months you're back to normal. So the common explanation-that your symptoms are due to low estrogen-is wrong. Your symptoms are actually caused by fluctuations of high and low estrogen. This also explains why you can't just get a blood test, as some doctors suggest, to tell if you are in perimenopause. Because your FSH goes up with menopause (once your periods have stopped for a year), some doctors will measure your FSH level in perimenopause, hoping to determine whether or not your symptoms are related to menopause. If your FSH is low, they tell you you're not in menopause and they don't know what your symptoms are from. If your FSH is high, they say you're menopausal-even if you're still menstruating.

Are they crazy? No. They simply don't understand perimenopause. A study in 1994 confirmed that perimenopausal women show varying patterns. Some women in the study still menstruated, even with increased levels of FSH. Some had increased FSH and normal to low estrogen. Some continued having cycles and had abrupt fluctuations of both FSH and estrogen. Some had typical postmenopausal levels one month and typical premenopausal levels the next month. So testing FSH isn't a really definitive tool for determining your menopausal status.

If you've stopped menstruating for several months, the FSH test might be a little more useful for determining if you've really gone into menopause. But even then it's not 100 percent accurate. Another study found that 20 percent of women who have no period for three months start having their cycles again. I've had patients with breast cancer who were thrown into menopause by their chemotherapy treatments, missed three or four months of periods, and showed high FSH levels-and then got their periods back. There's no foolproof test to determine menopause. The only way we can really do that is the good old-fashioned way. If you haven't menstruated for a year, you're menopausal.

Copyright © 2003 by Susan M. Love, M.D., with Karen Lindsey.

About the Author

Susan Love, M.D., is an adjunct professor of surgery at UCLA and the president of the Susan Love, M.D., Breast Cancer Foundation, a nonprofit organization dedicated to the eradication of breast cancer. She is the author, with Karen Lindsey, of the renowned Dr. Susan Love's Breast Book. She lives in Los Angeles.

Karen Lindsey is the author of Divorced, Beheaded, Survived: A Feminist Interpretation of the Wives of Henry VIII.