PMS, or perimenstrual syndrome, is a condition determined by the changes in mood and behavior that are connected to the changes in hormone concentrations during the menstrual cycle. Since the symptoms do not only occur before menstruation, the term perimenstrual (around menstruation) will be used here. There is no consensus yet about the exact cause(s) of the symptoms, although it is fairly certain that hormones have something to do with it.

• Progesterone?

Since most changes occur in the late luteal phase, when the progesterone concentrations are low, it has been stated that this hormone plays a role of importance. However, studies have shown that there is no consistent difference in progesterone concentration between women with or without PMS. What has been noticed, is that the progesterone concentration women with PMS are higher 10 days before menstruation. A possibility is that women with a higher initial concentration of this hormone are suffering from withdrawal symptoms.

• Estrogen?

Estrogen has also been implied as one of the possible causes of PMS. Storing the estrogen in the limbic system could be responsible for emotional and other manifestations of the neural system that are often associated with PMS. However, so far no consistent connection has been found between the hormone concentrations and the physiological symptoms of PMS. Furthermore, the hormone concentrations show no difference between women with mild and women with severe symptoms.

• The whole cycle?

Than what causes PMS? There is evidence that prohibiting the entire hormonal cycle to take place, eliminates the symptoms. It is possible that the sensitivity for steroid hormones changes during the menstrual cycle in women with PMS. The symptoms would than indicate an abnormal response to a normal quantity of hormones. Maybe sensitive women have more or different subtypes of receptors? These possibilities have yet to be researched.

• Food?

Through nutritional intake, hormones can also affect the mood of a person. It seems that women with PMS ingest more carbohydrates during the luteal phase, which increases the availability of tryptophane, a precursor of serotonin. It also appears that more meals are eaten, while the intake of proteins decreases. Furthermore, it seems that women with PMS often suffer from calcium deficiency and calcium supplements seem to lighten several symptoms.

All these data suggest that several hormones are involved at several levels in causing PMS. To identify the exact composition of endocrine events that are responsible for the syndrome, further research is required.