Premenstrual Syndrome (PMS) Causes

Premenstrual syndrome occurs during the luteal phase of the menstrual cycle. This phase occurs immediately after an egg is released from the ovary and lasts from day 14 through day 28 of a normal menstrual cycle (day 1 is the day your period begins).

During the luteal phase, hormones from the ovary cause the lining of the uterus to grow thick and spongy. At the same time, an egg is released from the ovary. If the egg meets sperm, it may implant in the lining of the uterus and grow. At this time, the level of a hormone called progesterone rises in the body, while the level of another hormone, estrogen, begins to drop. The shift from estrogen to progesterone may cause some of the symptoms of PMS.

• At first, some medical professionals believed that changing progesterone levels alone could account for a woman’s mood, behavior, and physical changes during the luteal phase (or second half) of the menstrual cycle. Progesterone interacts with certain parts of the brain that deal with relaxation. Newer studies suggest that other hormones and chemical changes may also be at work.

• For example, women develop deficiencies in a part of their nervous system called the endorphin system. Endorphins are "feel good" hormones. Normal levels contribute to cheerful, happy moods and also make people less sensitive to pain. (Drugs such as heroin and morphine act like super endorphins.) A small amount of these "feel good" endorphins usually circulate in the body, but these levels drop during the luteal phase of the menstrual cycle. In some women, falling endorphin levels may lead to nausea, jumpiness, and various types of pain.

• Many women with premenstrual syndrome retain water. This may occur because of cycling in hormones that affect the kidneys, the organs that control the balance of water and salt in the body. Fluid overload may cause some of the symptoms of PMS, especially swelling and weight gain, and may also aggravate some negative self perceptions and thus worsen emotional symptoms at this stage of the menstrual cycle.

• Diet may also be a factor in PMS. Progesterone, which affects insulin and levels of blood sugar, may affect alcohol tolerance and trigger the craving for sweets, especially simple sweets like candy and soda, that some women notice during the premenstrual phase. Such sweet foods break down very quickly in the body, so that blood sugar first goes up and then drops down low. Episodes of low blood sugar may contribute to both crying spells and the irritability that are part of PMS. Additionally, low levels of vitamin A, vitamin B6, and vitamin E may play a role in PMS.

• Hormonal cycling also affects the level of serotonin, a brain chemical that regulates many functions, including mood and sensitivity to pain. Compared to women who do not have PMS, some women who experience PMS have lower levels of serotonin in their brains prior to their periods. (Low serotonin levels are commonly associated with depression. Popular antidepressant medicines such as fluoxetine [Prozac] and paroxetine [Paxil] lift depression by raising levels of serotonin in parts of the brain.)

• Another theory explaining PMS involves inflammatory substances called prostaglandins. Prostaglandins are produced in the areas where PMS symptoms originate, namely, breast, brain, reproductive tract, kidney, and gastrointestinal tract. This suggests they may play a role in problems such as cramping, breast tenderness, gas, diarrhea, and constipation.

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