Causes:

Researchers are still uncertain about the causes of premenstrual syndrome. Fluctuations in gonadal hormones (progesterone or estrogen) and brain chemicals may play a role although their exact significance is unclear. Hormonal levels seem to be the same in women whether or not they have premenstrual syndrome. It is possible that women with premenstrual syndrome are somehow more responsive to these changing levels of hormones.

The Hypothalamic-Pituitary-Adrenal (HPA) System

The hypothalamic-pituitary-adrenal (HPA) system controls reproduction, appetite, and feelings of well-being. The HPA is also involved in regulating the stress response. A number of reproductive hormones and neurotransmitters (chemical messengers in the brain) play important and complicated interrelated roles in the activity of the HPA system. Disruptions in these chemicals may be important in PMS and premenstrual dysphoric disorder (PMDD).

• Reproductive hormones. The two important female hormones, progesterone and estrogen, are at their highest levels during the premenstrual period. An abnormal response to progesterone, more so than estrogen, may be the primary factor in PMS.
• Neurotransmitters. Each hormone is involved in the regulation of two neurotransmitters, serotonin and gamma-aminobutyric acid (GABA). These brain chemicals have properties that appear to protect against PMS symptoms.
• Stress hormones. Stress hormones include cortisol and norepinephrine.

The exact roles and relationships of any of these substances in PMS or premenstrual dysphoric disorder (PMDD) are still unclear. Evidence increasingly suggests that cyclic fluctuations in some of these hormones -- not whether they are high or low -- may be the important factors in premenstrual problems.

Other Factors

Calcium and Magnesium. Calcium and magnesium help nerve cells to communicate and blood vessels to widen and narrow. Imbalances in these minerals may contribute to PMS.