The term premenstrual syndrome was coined in 1931, when researchers first suggested that the condition was due to a hormonal imbalance related to the menstrual cycle. More recent studies have documented that PMS does, in fact, occur only during the childbearing years between puberty and menopause and subsides during pregnancy. PMS can also affect women who have had their uterus removed, leading researchers to conclude that the uterus is not part of the problem.
Despite these clues and the recognition of PMS as a legitimate medical concern, researchers have been unable to find a cause. Even today, no one knows for certain what triggers PMS, though a number of theories have been advanced.
Much of the research has focused on the hormones estrogen and progesterone, which are produced by the ovaries and are known to interact with certain brain chemicals. At about day 5 of the menstrual cycle, estrogen signals the lining of the uterus to grow and thicken, in preparation for receipt of a fertilized egg. Once an egg is released from one of the ovaries at mid-cycle, about day 14 of a 28-day cycle, progesterone production begins, causing the release of nutrients and the swelling of blood vessels to prepare for pregnancy. If the egg is not fertilized, the uterine lining and the egg are shed in menstruation.
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The Progesterone Connection
PMS coincides with the final enrichment of the uterine lining in preparation for arrival of a fertilized egg (see "A" at left). Not coincidentally, this phase of the lining's growth depends on increased levels of the hormone progesterone, which begins to appear as soon as an ovary releases its egg. In addition to its effect on the uterus, the extra progesterone is thought to have a damping effect on certain chemicals in the brain, possibly accounting for the agitation and mood swings that often accompany PMS. But the connectionif there is oneis still far from clear. Many doctors find that additional progesterone, taken as a daily shot or suppository, helps to reduce symptoms of PMS. Whatever the truth of the matter, this much is certain: If conception fails to occur, progesterone levels decline precipitously, and the hormone-starved uterine lining sloughs off in the monthly menstrual flow. During the following 2 weeks, when progesterone levels are low and the lining is relatively lean (see "B" at left), PMS symptoms generally abate. |
Thus, estrogen, which interacts with important brain chemicals affecting your mood and energy, dominates the first half of the menstrual cycle, while progesterone, which tends to suppress the actions of these brain chemicals, is more prevalent during the second half. Researchers found that temporarily reducing levels of both hormones in a group of PMS sufferers relieved their symptomsand that reintroducing the hormones prompted a return of the symptoms.
Still, even though the hormones appear to be a contributing factor, they are not believed to be the actual cause of PMS. Levels of the hormones seem to be normal in women who suffer the problem. And to confound the issue further, one major study found that women with PMS continued to show symptoms even after their menstrual cycles were artificially "reset" with medication. Researchers are studying the possibility that some unknown outside factor disrupts the normal interaction of estrogen and progesterone with chemicals made in the brain to cause some PMS symptoms.
One theory links fluctuations in the levels of serotonin with PMS. Serotonin (a byproduct of L-tryptophan, an essential amino acid found in many foods) plays several important roles in the body: it helps regulate sleep and menstrual cycles as well as the appetite. Some researchers speculate that low levels of serotonin may underlie PMS, throwing off the delicate timing of ovulation and prompting the restlessness and food cravings so often experienced by women with PMS.
Other theories proposed by researchers include: a deficiency of endorphins, the chemicals in the brain that create a "natural high"; defects in the metabolism of glucose or vitamin B6; low concentrations of zinc in the blood; fluctuations in prostaglandins, a family of hormone-like compounds found in most body tissue; low magnesium levels; an imbalance in the body's level of acidity; and chronic candidiasis, a vaginal yeast infection.
As of yet, little conclusive evidence exists to support any of these theories, making a definitive cure difficult, if not impossible. But research has shown that PMS responds well to a variety of treatments and that most women can minimize its effects by understanding and carefully managing their symptoms.
